Abstract: The calculation method of neutron noise power density spectrum for PWR nuclear power plants is analyzed. By using this method, the power density spectrum of noise neutron is calculated on the basis of long-term internal vibration monitoring system in nuclear power plants. Therefore, the power density spectrum characteristics of noise neutron for PWR nuclear power plants of million kilowatt is analyzed with different power and different fuel cycles. The results show that it can recognize the internal vibration behavior of PWR nuclear power plants through the analysis of power density spectrum characteristics, which can provide a basis for internal state analysis of PWR nuclear plants.