The invention relates to a multi-purpose sit-up board. The multi-purpose sit-up board comprises a front foot stand and a rear foot stand, wherein the front foot stand is formed by fixing a front cross bar and a front upright post, the rear foot stand is formed by fixing a rear cross bar and a rear upright post, the front cross bar and the rear cross bar are connected in a horizontal insertion manner and can be subjected to expansion and contraction adjustment, the insertion position is locked through a fastener, a seat cushion is horizontally fixedly connected above the rear cross bar, a backrest is arranged at the rear side of the seat cushion, the bottom of the backrest is adjacent to the rear side of the seat cushion and is hinged to the rear foot stand, an adjustment part for adjusting the angle between the backrest and the seat cushion is arranged between the backrest and the rear foot stand, lower knee supports are arranged at the front side of the seat cushion, lower foot supports are arranged at the front lower sides of the lower knee supports, a leg strength training mechanism and a boxing handle are further arranged on the front foot stand, and tension ropes are arranged on the front foot stand and the rear foot stand. The multi-purpose sit-up board is simple in structure and rich in exercising functions, and the angle of the backrest can be adjusted conveniently.