Domestic research pays insufficient attentions to the cooperation pattern of litigation, which is the common trend of civil litigation development in different countries at present.

This paper discusses the categories for CPA to perform the litigation support, the rights and duties for expert witness, the occasions for witness.

The author has,from the situation of China medium and small shareholders rights damages,analyzed the main reasons for and the situation of medium and small shareholders rights damages in Company Law and Securities Law,and compared China direct action and derivative action,individual action,joint litigation and representative action.

The article analyzes the reasons of the Supreme People s Court of China s non-adoption of American class action from legal,economical and political perspectives,and suggests that there are three limitations in the application of joint litigation to tort action of securities.

It is controversial that the Civil Procedure Act of the PRC and the Judicial Interpretation define representative action in Article 54 of the Act as joint action.

However,class action has its unique institutional value and advantage than traditional joint action.

An important one of those reasons is that some cases, which should be or can be handled in joint action, were separated into single cases which results in repeated work of courts, expansion of litigants\' legal cost and inconsistent judgments.