Abstract: Based on the number-rule of establishing the party organizations, this paper uses FRDD approach to test the causal relationship between the party organizations and the environmental investment of private enterprises. (1) By controlling the endogenous problem, it is found that the establishing party organizations can significantly improve the environmental investment of the enterprises, and OLS approach may underestimate the role of party organizations; (2) "Supervision and Guidance" is the important mechanism for the party organizations to play a role, which is manifested in restricting private enterprises to comply with the government environmental protection policies and regulations; (3) The role of party organizations in promoting investment in environmental protection will be positively moderated by the "party membership" of the private entrepreneurs; (4) The stronger the external environmental protection constraint is, the stronger the promotion effect of the party organization is. The conclusion of the study provides useful reference for improving the environmental governance system of the private enterprises, and helps to expand the understanding of the social value of "Non-Public Organizations' Party Building".

Key words: private enterprises, environmental protection investment, primary party organizations, fuzzy RDD