Abstract: In order to press Soviet to join the war against Japan, the U.S, without the Chinese agree,concluded Yalta Secret Contract with Soviet and Britain, which damaged Chinese sovereignty. China tried to pry content about this secret agreement through multiple ways . China had got the exact content though friendship between Wellington Koo and Leacy. To prepare the negotiation between two countries, Chiang Kai-shek had several talks with Soviet Ambassador to China. In case Soviet damage Chinese sovereignty, T.V. Soong had several discussions with Wellington Koo. Koo suggested to delay the negotiations as possible. Chinese delegation list was a focus both for America and Soviet. Wellington Koo was exclude the list just before the delegation head out.