Based on systematic analysis of repeatedly measured gravity data in the Linfen-Shanxi border area combined with deep crustal structure data, evolution characteristics of the gravity field in the Yuncheng Saline Lake, Shanxi province before and after the M_L4.9 earthquake on March 12, 2016 are discussed. The dynamic patterns of the gravity field clearly reflect the dynamic change of gravity field and the evolution process of M_L4.9 earthquake, that is quasi-homogeneous state-non homogeneous state-earthquake occurrence-post-quake recovery. In addition, gravity variation characteristics and their relation to the earthquake are analyzed.