Lionel Messi, David Villa and Pedro Rodriguez all scored as the Spanish champion put some extra distance between itself and closest rival Madrid, which couldn't break a stubborn defensive Deportivo despite Cristiano Ronaldo and Emmanuel Adebayor both hitting the post on late chances.
"Obviously it's a step backward," Madrid goalkeeper Iker Casillas said.
Barcelona, whose sole defeat of the season came in September, has 68 points to Madrid's 61 with 13 game to play.
"Seven points is not definitive," Madrid coach Jose Mourinho said. "We're going to continue on, and that's it." The absence of Xavi Hernandez, Carles Puyol, Daniel Alves and Victor Valdes made little difference at Son Moix Stadium as Barcelona overcame early pressure by the hosts before Messi headed home his league-leading 26th goal in the 38th minute.
Seydou Keita scooped into the area for the Argentina forward, who headed the pass forward before using his head again to guide over goalkeeper Dudu Aouate for his 42nd goal of the season.
Villa reached Sergio Busquets' well played long-ball before Aouate and after rounding the Israel goalkeeper rolled home his 17th of the season. The Spain striker's 21st overall matched the number scored by Zlatan Ibrahimovic for Barcelona all of last season.
Pedro's 13th goal was a long-range shot in the 66th that dipped over Aouate into the top of goal.
"There's still a lot of league left, we still have to go to Valencia, to Villarreal, to the Bernabeu, a lot to go," Barcelona coach Pep Guardiola said.
Madrid struggled to break Deportivo's defense and spent much of the first half testing Daniel Aranzubia's goal through long-range efforts by Kaka, Xabi Alonso and Mesut Oezil that all missed high. Ronaldo also had a first-half goal waived away offside.
Kaka, making a rare start, was active for many of Madrid's buildups while Karim Benzema was also a danger as he forced Aranzubia into a save in the 24th.
Ronaldo pressed for the winner but Aranzubia pushed the Portugal forward's dangerous free kick wide in the 77th before substitute Adebayor finally beat the Deportivo 'keeper but watched his volley come back off the near post.
Ronaldo then beat Aranzubia with a cross-goal shot in the 82nd but found the same post, with Aranzubia deflecting Angel Di Maria's shot from the rebound wide of the other post.
Benzema then missed a clear chance in the 85th as the France striker fanned on Ronaldo's centering pass.
"Who can talk about justice in football - you have to put the ball into goal," Mourinho said. "They played their game and had some luck, but they worked hard. If they played like that every game they'd be in the European places - you have to ask why they don't always play like that against us." Earlier, Atletico Madrid twice rallied to secure a 2-2 draw against Sevilla and Espanyol beat Real Sociedad 4-1 to end a four-game losing streak. Also, Sporting Gijon and Zaragoza drew 0-0 in a match of relegation-threatened teams.
Sevilla scored first at Vicente Calderon Stadium when Alvaro Negredo volleyed a rising blast past goalkeeper David De Gea in the 41st minute.
Koke scored on his Atletico debut after the young forward met Diego Forlan's long ball in the 47th sending a header out of the reach of Javi Varas.
Sevilla was ahead again in the 67th through Ivan Rakitic Jose Antonio Reyes equalized nine minutes later by slipping past the defense before slotting past Varas.
Varas denied Sergio Aguero twice from close range soon after as Atletico avoided slumping to a fifth loss in six.
Negredo found the crossbar late as Sevilla stayed five points behind Espanyol.
Espanyol provisionally moved two points ahead of Athletic Bilbao into fifth at the Cornella-El Prat where Luis Garcia found Alvaro Vazquez in the 41st with a quickly taken free kick before his try was helped into goal by defender Deniel Estrada.
Estrada made up for the opener with an equalizer two minutes later, but Sergio Garcia put Espanyol ahead for good in the 54th. Jose Callejon and Javier Marquez added the insurance for Espanyol as Sociedad slipped one point behind Sevilla in sixth after its two-game winning run ended.
Sporting stayed one point ahead of Zaragoza, which was 18th in the last relegation place.
