Seismic data collected by Shanxi Digital Seismic Network during a six-year time period were used to compute crustal thickness using the receiver function method and H-k search. The results show that at the northern margin of Pingyao Basin in Shanxi region, there exists a transition belt along the line between Wenshui and Jinzhong, called Jinzhong transition belt. The belt acts as a dividing line between the south thin crust (about 37~40 km) and the north thick crust (about 41~45 km) trending in NEE direction. The authors consider this transition belt being related to early precambrian basement structure and an important tectonic boundary inside the North China Craton.