The public interest could be classfied as group public interest and social or collective public interest by subjects of the public interest litigation. The former can be treated as the interest of the individuals,while the latter represents the interest of the society at large which,being formed by the collective interest,could not divided by individuals. Representatives who invoke public interest in environmental law disputes do so in either of two capacities. Firstly,such representative can sue on behalf of a class of victims,which may be called public interest environmental litigation. The second type is where the representative sues on behalf of a society as a whole,which may be called environmental litigation. Both of them have their own theoretical foundation respectively.On the one hand,this paper argues that the former instance is in fact private interest litigation or tort action because it is based on the enforcement of private rights of a closed group.On the other hand,an action on behalf of a society is truly based on public interest as it aims at national or human common interest.