Teacher collaboration has gradually become a common idea in the reform of teacher education all over the world. However, up to now, the current situation of teacher collaboration is still isolated and conservative to a certain extent. How to avoid being mere formality and promote the development of teachers' cooperative practice effectively has become an urgent problem for educational researchers and practitioners. Based on the data of TALIS 2018, this study focuses on the impact of teacher cooperation on teaching practice in China and the United Kingdom, with teacher self-efficacy playing the mediating role. Above all, SPSS 23.0 was used for data preparation, descriptive statistics, and Pearson product difference correlation analysis. Then, maximum likelihood estimation and robust standard deviation (MLD) were applied to estimate confirmatory factor analysis and structural equation model through Mplus 7.4. In addition, bootstrap self-help sampling method was adopted to test the mediating effect. About the direct effects of teacher collaboration on teaching practices, the results indicated that exchange and co-ordination was positively related to clarity of instruction in both China and England while professional collaboration was not significantly related to clarity of instruction in the two countries. In terms of the mediating role of self-efficacy between teacher collaboration and teaching practices, the study revealed the indirect effects of professional collaboration on three sub-scales of teaching practices exist via teacher self-efficacy in both China and England. Theoretical and managerial implications regarding using teacher self-efficacy as a mediating variable to examine the effect of common collaboration forms on specific teaching practices were discussed. Limitations and further research were also offered.