In order to clarify the effects of union practice and teacher ethics construction， 504 teachers of ten universities in Anhui were taken as case samples， and the path coefficients between variables were solved with the help of structural equation model to measure the direct and indirect effects of participation， education， maintenance and construction in union practice on teacher ethics construction. The results show that the participation， education and maintenance functions are positively correlated with the construction of teacher'' ethics. The maintenance and education functions have a more significant effect on the construction of teacher'' ethics， while the construction function has no significant effect. The trade union practice is significantly related to the atmosphere of appraisal relations and the construction of teacher'' ethics in colleges and universities. The atmosphere of appraisal relationship plays an intermediary role in the practice of trade union and the construction of teacher'' ethics in colleges and universities.