Abstract: Diesel engine cylinder head is one of the core components of marine diesel engine. The valve guide is the guiding device of the diesel engine valve. Accurate assembly can ensure that the valve can make straight reciprocating motion accurately. The valve guide and cylinder head generally adopt interference connection. Therefore, it is very important to ensure the assembly quality of the valve guide and the cylinder head. This paper mainly analyzed the press-fitting force and the stress and displacement changes caused by the valve guide and cylinder head assembly process under different interference conditions, and used the inner diameter of the valve guide of the contained part as the optimization parameter to optimize. Under the conditions of meeting actual working requirements, designed the optimal valve guide inner diameter size, and got the best fit size of the two interference fits, so as to provide the valve guide with the smallest pressing force, stress and the best interference pressing into the cylinder head, which provides a theoretical reference and guides actual production.