The invention aims to provide a design method of the bolt connection of the engine, thus shortening the development period of the bolt connection structure of the engine and reducing the development cost. The design method of the bolt connection of the engine is as follows: according to the performance parameters of the engine and the structural parameters of the parts of the engine, the limit working condition of the engine is used as the boundary, the connection pretightening force for connecting the important parts is calculated; bolts are selected according to the connection pretightening force, the final result is checked; and a reasonable tightening method is finally determined to ensure that the connection structure of the bolts and the parts of the engine can satisfy the requirement of the limit working condition the engine. By using the method of the invention, before a sample part is tested, the proper bolts can be selected and the reasonable tightening method can be determined for the connection of the important parts of the engine through calculation, thus avoiding various problems caused by the connection of the bolts in the test, increasing the development efficiency and reducing the development cost.