Using the digital earthquake data in Jiangsu Province and its adjacent area from January 2001 to April 2014，the paper studies the focal mechanism of 149 small and moderate earthquake cases in the Maoshan fault zone and its adjacent area with the combination of motion with amplitude ratio of P-wave and S-wave. The analysis of the characteristics of the focal mechanism solution shows that the type of the small and moderate earthquake in the study area is dominated by the strike-slip type with some normal fault type. The thrust earthquake is comparatively rare. The predominant orientation of P and T axes is NEE-SWW and NNW-SSE direction respectively. With the LSIB method，the stress tensor in the study area is inverted with the focal mechanism of 149 earthquake cases. The results indicate that the maximum principal compressive stress orientation angle S1 is 254.2°，the angle of depression is 2.6°. The minimum principal compressive stress orientation angle S3 is 163.9°，the angle of depression is 9.5°. In order to prove the reliability of the stress tensor，we use the focal mechanism solution of ML≥3.5 since 1970 to invert. The maximum principal compressive stress orientation angle S1 is 252.4°，the angle of depression is 8.4°. The minimum principal compressive stress orientation angle S3 is 160.4°，the angle of depression is 12°. The stress tensor inverted by the data of the two focal mechanism solution is very close. The solution of stress tensor indicates the Maoshan fault zone and its adjacent area is mainly under a modern tectonic stress field of NEE-SWW direction horizontal compressive stress and NNW-SSE direction horizontal tensile stress.