An automobile tailgate made of resin-based composite material, which includes an automobile tailgate outer panel, a tailgate window edge, a vehicle window inner frame, a tailgate license plate frame, an automobile tailgate inner panel, a tailgate hydraulic cylinder mounting support, and an inner panel reinforcement Ribs, tailgate latches, inner panel weight-reducing holes, tailgate hinge mounting holes. It is made of large-tow carbon fiber or glass fiber material, combined with low-viscosity resin, using resin transfer molding (RTM) process. The weight of the tailgate is further reduced through the topologically optimized weight-reduction holes on the inner panel of the tailgate. The strength and rigidity of the inner panel are enhanced through the reinforcing rib at the bottom of the inner panel of the tailgate. Use the tailgate hydraulic cylinder mounting brackets, tailgate latch and tailgate hinge mounting holes to mount composite automotive tailgates to the vehicle body. Due to the use of fiber-reinforced composite materials with high specific strength and specific stiffness, combined with the modular and lightweight design concept, the weight of the vehicle is greatly reduced, the number of parts of the tailgate is reduced, and energy saving and emission reduction are realized.