Abstract: In this paper, average seismic wave velocity ratios of Fujian Shuikou reservoir M_L4.8 earthquake sequence is determined using Multi-Station Methods.The correlation coefficient is high and the wave velocity ratio value is reliable.The wave velocity ratios before and after the main shock are analyzed.The result shows that in foreshock period the wave velocity ratios experienced a process of relative stable-low abnormal values-rebound-accelerated rise-high abnormally value-main shock occurrence;during the aftershock period, the wave velocity ratio is higher than before, low abnormal values increase, and the differences have increasing trend.