كتب : Hatem Maher
Deportivo defender Hector scored an own goal to put Real ahead before Brazilian striker Ronaldo doubled the lead in the first-half.
Two strikes by Sergio Ramos and Julio Baptista in the second period ensured the win for Los Meringues.
Real Madrid are in second place of La Liga table with 57 points, 11 adrift of leaders Barcelona.
The two arch-rivals clash next week in a game that can either keep the title in Barcelona for the second successive season or spark Real’s hopes into life again.
Real were in front as early as the ninth minute as David Beckham's free kick deflected off Hector's body and went into the back of the net.
Ronaldo, who ended a seven-match goal drought last week against Zaragoza, shined again for the Real, sending a warning message to Barca before traveling to Catalonia for the anticipated game.
The unmarked Ronaldo extended the lead eight minutes before the break with an easy tap in after receiving Robinho's low cross inside the area.
Beckham dished out his second assist of the game in the 70th minute as swung a fine free-kick that Spanish international defender Ramos headed home.
Baptista completed the rout eight minutes from time when he stepped up to deliver a stinging free-kick that sailed over the bar and left Deportivo keeper Jose Molina helpless.
In other matches, Celta Vigo beat Mallorca 2-0, Espanyol tied Alaves 0-0, Getafe defeated Real Sociedad 2-1, Sevilla edged Valencia 1-0 and Real Zaragoza were held to a goalless draw with Racing Santander.