Abstract: In this paper, three aspects of coseismic response to two strong earthquakes in Taiwan's Hualien area in 2009 are studied: delay time of surface wave, maximum deformation amplitude and lasting time of coseismic response.The result shows that the time delay of surface wave is the same to earthquakes at the same place;the lasting time of the coseismic response is relate to the resolution ratio of the observation instrument;the amplitude of the coseismic response is positive correlated with the magnitude of the earthquake.The coseismic responses are mostly high-frequency impulse and sometimes accompanied with phase step.The result may helps us get a better understanding of the performance of digital observation instruments, provides us a way to study short-impending anomaly prior to earthquakes.