Abstract: The successive legalization of environmental civil public interest litigation and environmental administrative public interest litigation has fostered a process of competition for maintaining environmental public welfare through litigation,and triggered a real problem of mode selection. The mode selection of "developing" environmental administrative public interest litigation and "suppressing" environmental civil public interest litigation is rooted in the academic community's taboo against the court's environmental regulation function. In fact,in the "night watchman state","welfare state" and "risk society",The court plays a fundamental role in resolving private litigation,at the same time,it plays the role of the regulator and Substitutor of environmental regulation according to social changes. The role of the court as a substitutor of environmental regulation can be proved from the "The Delegation Lottery Theory",the complementary nature of government and court makes the cooperative regulation a "second-best choice",which in turn determines the duality of environmental administrative public interest litigation and environmental civil public interest litigation should be the mode selection of environment public interest litigation.