Abstract: The subjects of civil evidence collection should include the parties, the counsels and the judges, but should not include the procurators.The parties should be dominant in the evidence-collecting process;the evidence-collecting acts of the counsels are important complement to the parties' ability to collect evidence;and the court's investigation and evidence collection is also essential.This paper defines the relationship between the subject and the object as that of division and cooperation: division is the prerequisite and cooperation is the essence and core.Cooperation in evidence collection process has double meanings, but the collaboration between the subject and the object is more meaningful.The legal basis for subject and object's cooperation obligations are different, but the common basis for cooperation lies in "duty to collaborate" theory.In the context of litigation model's transformation from "principle of debate" to cooperationism, the "duty to collaborate" theory lays a profound foundation for legitimacy.