CAP1000 reactor pressure vessel integrated bottom head was the integrated stamping molding of transition section and spherical bottom head forgings. The integrated bottom head forging was too deep, so it was difficult to control the quenching uniformity of head forgings opening and dome. In addition, the wall thickness of the integrated bottom head forgings was almost to 300mm. In order to make the forgings qualified performance, the overall quenching cooling effect of the forgings was need to be improved. In this paper, computational fluid dynamics (CFD) method was used to carry out the numerical simulation of mixing flow field of the integration bottom head in a quenching tank with screw. In order to improve the uniformity and speed of the flow in the vicinity of the head, different quenching schemes of the integrated bottom head were designed virtually and simulated. The placement of the head, the diversion device and the pumping device are all design factors. Eventually, the quenching scheme with bottom three-stage diversion and internal pumping with extended tapered guide was adopted for the deep and thick integration bottom head. The integrated bottom head with this quenching scheme was successfully trial-produced. And the tensile properties, impact properties and drop hammer results of each sampling position meet the product performance requirements with more margin.