The invention discloses a reactor pressure vessel integral top cover with an inner platform, comprising an integrated flange and a spherical head. A platform structure is integrally forged on the concave spherical surface of the spherical head, so that the concave spherical surface of the spherical head is gradually changed from a continuously gradual curved surface to a flat surface and then gradually changed to a continuous gradual curved surface. The platform structure is a solid body defined by a spherical surface and a circular plane, wherein the spherical surface of the platform structure and the concave spherical surface of the spherical head are integrally matched and connected, the circular plane of the platform structure is horizontally arranged, and the height of the circular plane in the vertical direction is higher than the height of the upper end surface of a flange in the vertical direction. The reactor pressure vessel integral top cover also comprises a tube socket mounting through hole penetrating through the spherical head and the platform structure, a tube socket inserted into the tube socket mounting through hole, and a circular tube socket weld, wherein the tube socket weld is arranged on the platform structure and covers the tube socket. The problem that vertical deviation of the tube socket caused by the traditional asymmetric weld is out of tolerance issolved.