Abstract: This thesis describes the design scheme,main capability parameter,relative technical reform and operation process etc.of the vacuum releaser of the primary circuit system of LingAo nuclear power plant.After the vacuum releaser of the primary circuit system being operated on site,the pressure of the primary circuit system can be below 0.02 MPa.abs,it can save about 30 hours in filling water and draining air process of primary circuit system.The design parameter and operation parameter of the vacuum releaser of the primary circuit system are better than the similar equipment of foreign country.This technique replaces a number of previous processes of static and dynamic draining air in the large-scale domestic nuclear power plant before filling water of no-fuel hydrostatic test,it is the first time to realize the vacuum releasing air in the large-scale domestic nuclear power plant before filling water of no-fuel hydrostatic test.