Abstract: The paper elaborates the work principles of nitrogen-style surge release valve and release volume calculationmethod based on the flow coefficient of pressure release valve, and analyzes the reasons why release volume calculatedwith the current method is much higher than the actual release volume. The principles of release volume calculation methodbased on the pipeline pressure test is analyzed, and an approximate method used in the release volume calculation ofwater hammer protection when water hammer occurs in a tight line transportation pipeline is developed, the results of theapproximate method are more accurate than that calculated by the commonly used method, providing a basis to the correctselection of release valve sizes and appropriate pressure release tank design, and ensuring the lead protection and effectivecontrol when water hammer accidents occur, avoiding damage to equipment and facilities.