从经典功率谱估计周期图法原理入手，从理论上分析了其存在的局限性，借助Welch算法对其进行修正。依靠Matlab强大的数值分析和信号处理能力，进行实验仿真，比较不同的窗函数，不同的数据长度对Welch法谱估计质量的影响，并分析了造成这些影响的原因。-The paper mainly introduces the principles of Periodogram method of classical PSD estimation,analyzes the deficiency of Periodogram method in theory,and makes use of Welch to amend Perodogram method. By the use of simulation in Matlab, the impacts of different window function and different lenghth of data on estimation quality of Welch are discussed and the reasons of the impacts are analyzed.