In this paper, based on the up to date global free-air gravity anomaly dataset (TopexV18.1), combined with existing velocity model and thermal parameters of lithosphere, the authors carried out thermal isostasy contrast studies for 10 secondary block units of North China. The results show that there are distinct differences both in the deep structures and thermal isostasy characteristics because of the various destruction of the bottom of North China Craton. The recovery relationship of topography and heat flow after deducting the gravity effect from the average seismic wave velocity indicates that there is very remarkable effect for the present topography. But the effect is not obvious in the Yanshan Uplifted zone and Jizhong Depressions block.