Based on Sobol method,AP1000 first cycle core key physical parameters such as power peaking factor,moderator temperature coefficient,control rod worth sensitivity analysis can be carried out by the Latin hypercube sampling of input design parameters such as fuel clad diameter,fuel enrichment.The results show that: AP1000 first cycle core key parameters are sensitive to fuel clad outside diameter,fuel assemblies with 1. 58%,3. 20%,3. 80%,4. 40% fuel enrichment,fuel pellet diameter,10 B line density of IFBA and guide thimble diameter.