In this study, an experiment is conducted for assessing the friction characteristics of a wet clutch on actual working conditions, to determine how various factors influence the friction coefficient in the actual working process of a wet clutch. Based on the experimental data of a wet clutch under different engagement conditions, a data surrogate model construction method is proposed for the friction coefficient. According to this model, the decoupling between different influencing factors of friction coefficient is realized, and their influence on friction coefficient is obtained. To reveal the change mechanism of the friction coefficient, a theoretical analysis model of the friction coefficient is established by using the elastic contact theory and the elastic fluid dynamic pressure lubrication theory. In addition, based on the constructed friction coefficient data surrogate model, the sensitivity of different influencing factors on the friction coefficient and the coupling relationship between the different influencing factors are studied.