The invention discloses a construction method of a filling-type base plate of a plate-type ballastless-free rail. The construction method comprises the following steps of: adjusting the states of the rail; mounting an injection bag; stirring and mixing resin; injecting and subsequently processing the resin; stirring and mixing with filling resin; filling in the injection bag under pressure; and solidifying into an insoluble immiscible fiber-reinforced plastic base plate to heighten the rail in a stepless mode. The filled base plate is fully and compactly filled and tightly combined without bubbles and layers; and solid matter favorably resists UV irradiation, coldness, hydrothermal aging and chemical corrosion, has suitable elasticity and mechanical strength, can realize the long-term stability of the long-distance rail surface after accurate elevation adjustment, and ensures the smoothness requirement of the plate-type rail of a high-speed railway. The invention has simple operation, rapidness and convenience and is particularly suitable for the field construction of the filling-type base plate of the plate-type ballastless-free rail in a severe cold area.