Barnet stayed top of the Conference after securing a sixth successive win.
Three goals in 10 first-half minutes did the damage after Giuliano Grazioli had hit the woodwork for the Bees.
Liam Hatch finished off a cross by Richard Graham before Grazioli got his eighth of the season and Hatch added his second with a well-struck volley.
Dean Sinclair netted the fourth before Gravesend's Manny Omoyinmi pulled a late goal back and Fleet defender Chris Moore received a second yellow card.
Barnet: Millard, Hendon, King, Yakubu, Clist,
Strevens (Dobson 85), Sinclair, Lopez (Bailey 82), Graham,
Hatch, Grazioli (Roache 77).
Subs Not Used: Tynan, Champion.
Booked: Strevens, Sinclair, Graham.
Goals: Hatch 36, Grazioli 44, Hatch 45, Sinclair 80.
Gravesend: Mitten, Protheroe, Shearer (Jackson 31), Moore,
Lovell, Drury, McKimm, Saunders, Surey, Essandoh (Omoyinmi 71),
Louis, Jackson (Sidibe 64).
Subs Not Used: Wilkerson, Gledhill.
Sent Off: Moore (89).
Booked: Surey, Moore.
Goals: Omoyinmi 88.
Att: 2,235.
Ref: M Harris (Lincolnshire).