Abstract: Nuclear reactor doubling time is an important parameter in nuclear reactor engineering. Reactor operator can know the reactor running state and control the reactor reactivity according the doubling time during reactor start-up and power-up process. In digital neutron monitoring system, the doubling time was calculated with the sampled and processed voltage signal which was proportional to the reactor power. In practical applications, the voltage signal often contains amount of measurement noise which causes a large uncertainty on the calculation result. In this paper, the sensitivity of nuclear reactor doubling time calculation was analyzed, and some relevant calculation examples were given.