Abstract: By use of mean focal mechanisn solutions from 12 stations and reliable those forsmall and moderate earthquakes,this paper is to discuss characterstic distributions of regional stress fields in the study area.The results indicate that the distribution of the stress field north of 32癗 in thisarea is characteristic of the North China block;south of 32癗,it is characteristic of atransition of the North China block to the South China one;souther Anhui is characterises of South China.These characteristics serve to define the southern boundary of the North China block.