Abstract: Tensile tests of specimens with different gauge lengths of multiple sorts of cold-rolled steel sheets were performed to solve the problem that the rules of specimen gauge lengths are not all the same and percentage elongations after fracture (A) are not comparable, resulting in the inconvenience of selecting materials for autos. Results show that, compared with the percentage elongation after fracture, percentage total extension at maximum force (Agt) is not related to the gauge length of tensile specimen, it is a inherent characteristic parameter corresponding to the point of tensile strength (Rm) on the tensile curve of material. With the development of computer-aided test technology, nowadays, the Agt parameter could be conveniently measured by cold-rolled steel sheet factories and auto factories. It is suggested that Agt, which is not regulated by specimen gauge length and reflectes the essential characteristics of plastic material, is the ideal index for evaluating the elongation rate of cold-rolled steel sheet materials .