Abstract: Determination of source parameters of small earthquakes from amplitude ratios of P and S is studied in this paper when the distribution of the regional seismic network is skew to the earthquakes. The distribution of stations of the seismic network was to one side of the 17 earthquakes chosen from among 39 earthquakes in the east part of Guangdong and south part of Fujian province. The distribution of stations was classified into three types according to their relative positions with respect to the chosen earthquakes and the experiments of artificial data were done. Excellent results were also presented in various unfavouable conditions by using the method.As to the 39 small earthquakes recorded by the network in east Guangdong and south Fujian province from 1982 to 1986, the results can be summarized as follows: Most of the fault planes of the earthquakes apear to be steep. Most of the principal compression stresses P and tensile stresses T are nearly horizontal, concentrating in the WNW-ESE direction.