The Tanlu ( Tangcheng-Lujiang) fault is one of the major faults in eastern China， which cuts across different blocks and controls the tectonic activity． Using the seismic data from China Earthquake Networks Center，we investigated the spatial variations of b-value in the Dabie- Sulu organic belt by calculating b-value of each grid ( 1° × 1°) from 1970 to 2010． The study shows that: the b-value is smaller in the Tanlu fault and its adjacent area，which might suggest that the major earthquake recurrence period is relatively long due to the less frequency small earthquake activity; in the both sides of Tanlu fault，b-value is higher at the edge of Sulu block and eastern part of Dabie orogenic belt; the b-value is higher in North China Central orogenic belt，and small earthquake activity which occurred along Central Orogenic Belt is frequent． Additionally，combined with geological and geophysical study，we find out that the b-value shows directly the relationship with the lithologic distribution，which informs us that seismic activity features closely linked the inhomogeneous media in the crust．