The invention provides a definition selection method for a non-orthogonal port in a special-shaped layout. The method is characterized by comprising the following steps of 1) determining a port line segment used for line connection in a master unit; 2) obtaining a rotation angle theta in attributes of non-orthogonal units; 3) performing rotation transformation on the port line segment of the master unit to obtain a transitional line segment; 4) obtaining a translation attribute relative to the master unit in the attributes of the non-orthogonal units; and 5) performing translation operation onvertexes of the transitional line segment to obtain to-be-wired ports of the non-orthogonal units. According to a wiring technical scheme, the port positions in the non-orthogonal units can be determined through unit names, port process layers, tag names and port directions in the master unit, thereby providing a basic condition for subsequent wiring.