A design method of cipher is provided. First, a database with a plurality of picture units is provided. Then, a part of the picture units of the database are selected to form a passing picture, and the passing picture is transferred to an encoder. The encoder selects at least parts of the picture units of the database to form a plurality of option pictures, in which a part of the picture units of the option pictures correspond with the picture units of the passing picture. A picture cipher system is also provided.