Used the seismic records collected in the magnitude 6.0 earthquake occurring in Yongsheng County, Yunnan Province, its velocity response spectrum was obtained by solving the motion equation of the single degree of freedom system with Matlab programming. The V/PGV was calculated and the coefficient response spectrum was analyzed. A series of 100 response spectrums, each 6 s period apart, were randomly selected for studying and divided into two categories according to the location peak of the response spectrums. By using the traditional method, several inflection points of the response spectrum were roughly judged and their coordinates were statistically calculated. K-S tests were performed on each selected inflection point group based on the method of three-parameter Weibull distribution. The test results for the selected reaction spectrum inflection point were acceptable, and the expected value of each inflection point was further obtained. Taking the expected value of several inflection points as the piecewise points of the design response spectrum, a four-step design response spectrum was proposed by using the least square fitting with the measured seismic response spectrum curve. The error analysis of the design response spectrum and the actual response spectrum verifies the correctness of the design response spectrum.