Abstract: On the basis of 269 small earthquakes recorded by the 24 stations of Jiangsu and Shandong digital seismograph networks, this paper studies the small-scale medium inhomogeneity of mid-upper crust beneath the middle segment of Tancheng-Lujiang fault zone by using the scattering S-wave envelope broadening method. The results reveal that strong inhomogeneity exists in the mid-upper crust beneath the middle segment of Tancheng-Lujiang fault zone, and the Tancheng-Lujiang fault zone is the boundary of the medium with different inhomogeneity strength and different inhomogeneity scale. The deep structures are strongly correlative with the boundary of the strong and the weak inhomogeneity. The results also show that the developments of the moderate-strong earthquakes are related with the distribution of the strong and the weak inhomogeneity bodies, and moderate-strong earthquakes generally occur at the transitional zone of the strong and the weak inhomogeneity bodies. The distribution characteristics of medium inhomogeneity in the mid-upper crust beneath the middle segment of Tancheng-Lujiang fault zone maybe relate with ultra-high pressure metamorphic belt, deep structures and magma activity.