Using the data of available geomagnetic stations in Sichuan and its adjacent areas as the research object,we applied Smooth pseudo-Wigner-Ville(SPWVD)method to calculate the time-frequency. Then we conducted retrospective analysis on the amplitude variation characteristics of geomagnetic stations in Sichuan-Yunnan region during geomagnetic stations near Kangding and Jiuzhaigou earthquakes and active and quiet periods of moderately strong earthquakes with a period of 4.4h after Z component filtering. It is found that before the 2014 kangding earthquake,7 geomagnetic stations near the epicenter had the abnormal phenomenon of synchronous high value in 4.4h amplitude,of which the amplitude of 5 stations was the highest value in the study period before the earthquake. Before the Jiuzhaigou earthquake,six stations near the epicenter had the abnormal phenomenon of relatively high synchronous value,among which the amplitude of three stations was the highest value in the study period. During the active period of Sichuan and Yunnan in 2014,the 4.4h amplitude synchronous anomaly was common in the geomagnetic stations in this region,with the largest number of stations and large amplitude,which is positively related to the occurrence intensity of medium and strong earthquakes in this period,showing short-term and imminent characteristics in time. During the moderate strong seismicity quiet period in Sichuan and Yunnan in 2018,the amplitude variation in 4.4h is relatively stable,and the abnormal amplitude is relatively small,then the maximum amplitude of synchronous anomaly increases and the number of abnormal stations increases during the active period. In summary,SPWVD time-frequency method is capable of processing and analyzing geomagnetic data,and the application of this method will be of significance for the prediction and analysis of regional seismicity of moderate-strong earthquakes in Sichuan-Yunnan region in the future.