Abstract: The documents collected from the Poyang Lake Region by Shanghai Jiao Tong University record a dispute between the Cao Clan based in Duchang county and Yang Clan based in Poyang county during the Qing dynasty. From 1776 to 1799，the two clans constantly disputed over the ownership of three lakes， which were located along the board of the two counties，and they even brought the case to Beijing. According to our study，however, the claimant，Cao clan had no legitimate claim over the disputed lakes. Even though the Cao clan depicted themselves as the victim，but in fact，they were trying to appropriate Yang clan’s property. This case shows that the civil justice of the Qing dynasty was committed to protect the property rights of the commoners;due to the protection of the state，the Cao clan，which was stronger，admitted the rights of the Yang clan，which was weaker. More importantly，the state was creative in solving the dispute:it firstly judged the rights and wrongs based on evidence，and then introduced market mechanism to achieve a win-win result. This approach was more effective in solving civil disputes than solely relying on law.