Abstract: In the process of replacing HPR1000 reactor detector, the first step is to position the reactor detector replacement above the detector. This paper proposes the positioning requirements of the reactor detector replacement firstly, and then analyzes the position system combined with the process of replacing reactor detector, and proposes the closed loop visual servo positioning scheme of reactor detector replacement. This technical scheme fulfills the position accuracy requirement, ensures the detector a small deflection angle during lifting and mitigates the wear of the mechanical seal joint .