The invention relates to a multi-layer coextrusion in-mold composite die. The multi-layer coextrusion in-mold composite die comprises a lower die body, an upper die body, a flange and two middle die bodies. The flange is connected with one side of the lower die body, one side of the upper die body and one sides of the two middle die bodies. A die lip is correspondingly arranged at the other side of the lower die body, the other side of the upper die body and the other sides of the two middle die bodies. Heating pipe holes are formed in the upper die body, the middle die bodies and the lower die body. Heating pipes are arranged in the corresponding heating pipe holes. A flow channel is formed between the upper die body and one middle die body, and a flow channel is also formed between the lower die body and the other middle die body. Adjusting bolts which are vertically placed are arranged in the upper die body and the lower die body separately. Damping bars are arranged at one ends of the adjusting bolts. An included angle of 90 degrees is formed between each damping bar and the corresponding flow channel, and the damping bars are connected with the corresponding flow channels. The other ends of the adjusting bolts are arranged outside the die.