Abstract: The calculations of loading patterns（LPs） in each cycle（first cycle,transition cycle and equilibrium cycle） have been completed using the SCIENCE nuclear code package.To meet the requirement of refueling cycle length for 2 years,the enrichment of fuel,the numbers of refueling assemblies and the LPs have been tested.‘In-out’ strategic has been used to reduce the neutron leakage.In first cycle,the higher enrichment fuel assemblies（FAs） have been loaded in the outer region of the core,while the lower enrichment FAs have been loaded in the inner region.In cycle 2,44 fresh FAs（4.95%） have been arranged in the core,44 old FAs have been discharged,while old FAs have been loaded in the outer region.In cycle 3,only FAs with 0,12 and 20 Gadolinium rods have been used.As the result,the design criterion for the maximum discharge burnup has been met.