Abstract: Taking the accumulator and filter in Taishan Nuclear Power Station as an example,the flange joint calculation method under pressure,temperature,external force and moment is introduced in detail in terms of operation condition,transient analysis and calculation model disposal.It especially considered that the flange and stud integrality may be affected at the transient when the temperature increases greatly,and the flange seal could be affected when the flange dish declining angle is too big resulting from the over tightened stud.The flange design calculation can be referenced in other engineer projects.