The invention provides a tool for switching a burnable poison assembly and a neutron source assembly in a nuclear power plant. The tool comprises a support frame, a lifting structure, a gripping structure and a position detection part, wherein the lifting structure is arranged at the top of the support frame; the gripping structure is arranged in the support frame, the bottom of the gripping structure is suitable for being connected with the assembly to be switched, the top of the gripping structure is connected with the lifting structure, and the lifting structure drives the gripping structure to move up and down; and the position detection part is arranged on the lifting structure and is used for acquiring the position of the assembly to be switched according to the moving distance of the lifting structure. By virtue of cooperation among the lifting structure, the gripping structure and the position detection part, reliable switching between assembly to be switched, such as the burnable poison assembly and the neutron source assembly, is realized, the position of the assembly to be switched is monitored in real time to ensure accuracy and reliability of the moving stroke of the assembly to be switched, and switching between the burnable poison assembly and the neutron source assembly is realized to meet the needs of related assembly operations in nuclear power daily work andoverhaul work.