Abstract: Flow velocity of gas has a significant influence on the corrosion of gas field. The article Judges the type of gas flow in Mo Xi gas field using Reynold criterion number and analyzes critical flow velocity of gas, which is the coefficient representing the capacity of the corrosive matter carried by fluid. The flow velocity of gas inside the gathering equipment in Mo Xin gas field is less than 1.5m/s, which is the real reason resulting in serious partial corrosion. If there is liquid existing in gas, only the fluid's flow velocity assuming mist flow in pipeline equipment is favorite to the corrosion protection of the equipment. Meanwhile mist flow combined with corrosion inhibitor will make the corrosion inhibitor diffuse evenly, thus increases corrosion control efficiency.