Abstract: Once defects occurrs on the components installed on the nuclear reactor basket（lower internals）, which requires repair, the curved surface for installation shall be accurately measured firstly. By analysis of the precise measurement technology and implementation process for the installation curved surface on the barrel for irradiation surveillance capsule support structures, it proved that the solution can achieve the purpose for space curved surface precise measurement underwater at high radiation conditions by the combined measuring device with high precision digital gauge, grating sensor and directional movement of the ball guide rail.