Abstract: As a protection method, mechanical over-speed protection makes a great contribution to the development of turbine. With the improvement of computer technology, the reliability and stability of I&C have been increasing, in contrast, the complex construction, oil loop, oil injecting test and actual over-speed test of mechanical over-speed bring inconvenience to the operation and maintenance of the power plant, also impact the grid connection time as well as the economy. Combined with the turbine technology development and utilization, this paper analyzes the improvement of AP1000 nuclear turbine overspeed protection system,and puts forward the improvement plan.