The Gate led at half-time courtesy of Ibrahim Olutade’s sixth minute goal.
Dan Ajakaiye rattled the post early in the second half before Ola Ogunwamide squeezed the ball underneath Margate goalkeeper Tom Wray to draw the Hornets level on 71 minutes.
The two sides meet again at the Fusion Aviation Community Stadium this evening for a place in the fourth qualifying round.
The winners of tonight’s tie will host Isthmian North outfit Gorleston in the next round on Saturday, October 12.
See some of John Lines’ pictures from the game on this page and the ones linked, and read Horsham manager Dominic Di Paola’s thoughts in the West Sussex County Times, out every Thursday.
9. FA Cup: Horsham FC come from behind to force replay against Margate - the match in pictures
Action from Margate v Horsham Photo: John Lines
10. FA Cup: Horsham FC come from behind to force replay against Margate - the match in pictures
Action from Margate v Horsham Photo: John Lines
11. FA Cup: Horsham FC come from behind to force replay against Margate - the match in pictures
Action from Margate v Horsham Photo: John Lines
12. FA Cup: Horsham FC come from behind to force replay against Margate - the match in pictures
Action from Margate v Horsham Photo: John Lines