As a remedy for breach of contract, specific performance system is embodied in domestic legislation and international legal instruments. CISG, UPICC and PECL, and other international legal instruments, as important outcome of the uniform substantive law in international trade, have had a significant impact on international trade, and have made the corresponding provisions on specific performance system. But there are some differences in the relevant provisions. Based on a comparative study of the specific performance system in CISG, UPICC and PECL, it is clear that what has been unified about the specific performance system and what is not unified. Suggestions are put forward to promote the further unification of the system. According to the relevant provisions of CISG, UPICC and PECL, improvement of specific performance system in China’s contract law is needed