Abstract: Manipulator crane is one of the key equipments which belong to the fuel handling and storage system（PMC system） in PWRs. In-core positioning is a prerequisite for the first fuel loading, and the security of reactor refueling. Single point positioning method is the prevailing method of reactor core positioning in the domestic PWRs. During the core positioning test with the single point positioning method, the problem that the dummy would bump against the lower internals appeared in a nuclear power plant. Through the innovative core positioning method—four points centre and average step length method, this problem was solved successfully. This paper analyzes the advantages and disadvantages of the single point positioning method and the four points centre and average step length method.