Abstract: This paper has done research on the optimization of core fuel management for units 1-4 of Tianwan NPP by KASKAD program package to unify the fuel management schemes. In the optimizing schemes, less varieties and quantities of fresh fuel assembles are used, however the average enrichment of new FAs is higher to increase the length of equilibrium cycle. All the safety parameters of the optimizing schemes according to the core calculation results satisfy the requirements of limiting values. The optimizing schemes are with good flexibility, and can increase the utilization of the fuel as well as increase the economic benefit of the plant, and have good engineering application value.