The first high tide of research on the Question of Hong Kong appeared in 1997 when Hong Kong returned. As an organic part of the Question of Hong Kong, there had been few scholars who paid attention to the cession of Hong Kong from the concrete example. This article inspect the mandate purpose of the Palestinian and the Elliot who take the mandate into action in order to reveal the status and function of Elliot in the cession of Hong Kong. This thesis will further analyze the internal reasons of the cession of Hong Kong from the aspect of Elliot breached diplomatic Mandate.