To address the complex correlation between wave height and wave period, a joint distribution study method based on a mixed Copula algorithm is proposed. This method selects three Copula functions for goodness-of-fit testing. Then, a mixed Copula function model is constructed to analyze the correlation between wave height and wave period. Finally, the EM algorithm is applied to solve the model's correlation coefficients and compute the joint distribution of wave height and wave period. The results show that the mixed Copula function provides higher accuracy than single Copula functions in describing the correlation between wave height and wave period.