The Piecewise Linear Representation of the amplitude spectrum is introduced using the PAA method in a semi logarithmic coordinate system. The automatic extraction of the lowest and upper frequencies for high-frequency attenuation is achieved by calculating the distance from the mean point to the straight line. Subsequently, the feasibility and effectiveness of the method were verified using 21 aftershock records of the Wenchuan earthquake received by the 51JYC station. Finally, combined with different high-frequency attenuation parameters κ₀, stochastic ground motion simulation was conducted for the 2013 Lushan M_W6.7 earthquake using 51JYC as the receiving station. The results show that there may be significant differences in the initial and cut-off frequencies of high-frequency attenuation for different records, which has a significant impact on the calculation of the κ₀ value. The peak ground acceleration (PGA), Fourier spectrum, and response spectrum of stochastic earthquake motion simulation are extremely sensitive to the κ₀. Furthermore, the law of their variation affected by the κ₀ value is consistent with the research results of many scholars, verifying the reliability of our random simulation. Therefore, it is believed that the method proposed in this paper for automatically extracting the initial and cut-off frequencies of high-frequency attenuation intervals can not only improve work efficiency, but also reduce the influence of subjective interpretation on the calculation results. This has certain reference and practical value.