利用怀来地震台水管仪的数字化观测资料，采用功率谱密度估计方法，在没有对资料去固体潮处理的情况下，准确获得2004年12月26日苏门答腊9.0级地震激发的0S2—0S38基频球型自由振荡，并与PREM模型的理论自由振荡周期进行对比，发现实测振荡周期与PREM预测的振荡周期吻合，除0S2、0S4、0S7振型的观测周期和PREM模型理论周期的相对误差大于0.3%外，其他振型的观测周期和PREM模型理论周期的相对误差大都集中在0.1%左右，同时检测到7个谐频球型振荡和10个环型振荡。可以从水管倾斜仪的观测资料中提取地球球型振荡信息，为地球自由振荡的研究提供一种新的仪器观测方法。

In this research, without dealing with the case of solid tide, we successfully detected 0S2 —0S38 free balloscillation excited by Sumatra earthquake on December 26, 2004 in the use of  observational data of the digital waterpipe meter in Huailai Seismic Station, with power spectral density estimation methods. Comparing with the freerunning period of PREM model theory, we found that, except for the relative value between the period of 0S2、0S4、0S7 and the PREM prediction is greater than 0.3%, the value regarding the vibration mode of the observation period and the PREM model were mainly focused on the relative error of about 0.1%. Also, we detected seven harmonic oscillation and 10 ring oscillation. In the use of observed data from waterpipe instrument to extract information of Earth oscillation, provide a new instrument method of observation for the study of the Earth′s free oscillations.