The invention discloses a double-triangular chord member-precast bridge surface board composite beam and a quick assembling method. The double-triangular chord member-precast bridge surface board composite beam comprises an upper chord steel pipe and a lower chord steel pipe, wherein the upper chord steel pipe and the lower chord steel pipe are arranged on the lower surface of the bridge surface board in parallel; a plurality of web steel pipes are arranged and are mutually connected to form a triangular structure to support the upper chord steel pipe and the lower chord steel pipe; a bridge surface board chute is also arranged between the upper chord steel pipe and the lower surface of the bridge surface board; the upper chord steel pipe is arranged in the bridge surface board chute; the bridge surface board slides on the upper chord steel pipe through the bridge surface board chute; the lower chord steel pipe is hinged and fixed onto piers on two sides of the bridge; the bridge surface board and the upper chord steel pipe are fixed through an Omega-shaped fastener. In a valley, the bridge surface board slides to a preset position on the upper chord steel pipe through the chute so as to be conveniently disassembled, installed and conveyed, and the defect of difficulty in the field construction of a traditional bridge structure is overcome; the integral structure design of the bridge is suitable for construction in special conditions including valleys and the like, composition construction members can be assembled on site, a manufacture technology is simple, and cost is low.