In China, for the long-distance pipeline system, usually both the design pressure for compressor station and pipeline comply with GB 50251:Code for Design of Gas Transmission Pipeline Engineering, which specifies the Maximum Allowable Operating Pressure( MAOP ) shall be equal to or less than the Design Pressure( DP ). However, the margin between the Maximum Operating Pressure( MOP ) and MAOP is not mandatory in this Code. For many years, domestic long-distance pipeline system generally leaves a margin of 0.15 MPa between the MOP( at compressor discharge line in compressor station ) and design pressure. But whether this margin is appropriate has not been demonstrated. By studying the standards of long-distance pipeline systems at home and abroad, it is found that the basis for limiting MOP is that the overpressure value of transient pressure under accident conditions shall not be greater than 10% of MAOP. The conventional practice of long-distance pipeline with 10 MPa design pressure has been verified using SPS software to simulate and analyze accident conditions. Moreover, considering the actual operating pressure fluctuations on site, recommendation is given for determining optimal MOP, which is of great significance to ensure the safe and economic operation of the long-distance pipeline system.