The geomagnetic field is one of the basic geophysical fields,and the seismomagnetic relationship has been laboratory tested.Many studies in China and abroad have reported abnormal geomagnetic variations prior to the occurrence of earthquakes.In this study,with the Wenchuan earthquake as our research object,we selected observation data from the Chengdu geomagnetic station for three periods (July 2007-June 2008 prior to the occurrence of the earthquake,July 2011-June 2012,and July 2012-June 2013 following the occurrence the earthquake).Using the same data processing method for each,we calculated the peak values of their power spectra in the low-frequency band.The results show some abnormal changes in the peak value of the power spectrum at low frequency from July 2007 to June 2008 at the Chengdu station,but no similar changes occurred during the other two periods (July 2011-June 2012 and July 2012-June 2013).To further examine the data,we used the same data processing method for the same periods with data from the Xichang geomagnetic station and observed no abnormal changes.Combined with our other research results,we found the abnormal change to be related to the Wenchuan earthquake,based on its regional characteristics,which was likely related to the epicenter distance.However,determining the generation mechanism of this phenomenon will require more data and further research.These results represent a significant contribution to the study of the seismo-magnetic relationship.