Abstract: Aiming at the problem of quality evaluation for resistance spot welding of hot stamping high strength steel, the dynamic resistance information of the normal welding spot, the welding spot with incomplete fusion, and splash welding spots extracted by the LabVIEW system were analyzed. A five-digit generalization method was proposed to set the threshold value. Results show that the dynamic resistance curves of the welding spot with incomplete fusion and the normal welding spot have obvious differences in the characteristic parameters such as the parameters of speed, falling range, ending value and effective value. When the splash welding spot happens, the dynamic resistance curve will drop sharply. The least squares fitting is performed on the dynamic resistance curve of the splash welding spot and the actual dynamic resistance curve and the fitting dynamic resistance curve is subtracted to calculate the root mean square values, namely, splash characteristic index. Therefore, on the basis of characteristic indexes, on-line evaluation of the welding quality is obtained and good results are achieved.