While the interpretation of the Expression of Intent has always been the core of Civil Law research, the methods of conducting such interpretation have once again caught the attention after China passes the General Principles of Civil Law. This thesis aims to first elaborate on the methods of interpreting the Expression of Intent and the elements of objective interpretation, then research on the literature and trials of Germany, Japan, and China, and finally analyze the deficiency of Taiwan's domestic law and the development of the law practice. The elements of interpreting the Expression of Intent in this thesis will be centered on the Rules of Expression, while targeting on the research of social common sense and the trade custom with personal point of view delivered.