Abstract: the authors use waveform records of 5 stations of Xiuyan, Yingkou, Benxi, Beizhen and Xinmin from digital seismic station network of Shenyang, Earthquake Administration of Liaoning Province, to calculate apparent stress of Xiuyan sequence of M_S5.4 earthquake occurred on Nov. 29, 1999. The calculated results from the five stations are well consistent, and change of apparent stress of Xiuyan sequence has notable common feature, i.e. low apparent stress phase before earthquake, high apparent stress phase while earthquake occurrence and adjusting and stable phase after earthquake, during this phase, the stress reduced gradually. That apparent stress increase before the M_S5.4 mainshock and maximum strong aftershocks of M_S5.1 show that apparent stress could be regarded as criterion of earthquake tendency before and after moderately strong earthquakes.

Key words: Xiuyan sequence, Seismic apparent stress, Earthquake tendency