Abstract: Issue preclusion validity is an effect in general use created in the former litigation court's judgement to the issue, which was once argued mainly by both parties in the former litigation, and was also tried and judged by the court, when the same issue as the main primarily settled question appears in the latter trial for the other claims. According to the role of the issue preclusion validity, the party in the latter litigation can't put forward the assertion and evidence that violates this judgement, and the latter court's judgement can't contradict it. Its theoretical basis is credit and fairness doctrine. It has important theoretical and practical function. China should bring in the theory of the issue preclusion validity.