The mechanical property of X80 longitudinally welded pipe, as part pipeline for second west-east natural gas transmission pipeline project, is disadvantageously affected by normal coating process of three layer polyethylene coating(3LPE). The low application temperature process of three layer polyethylene coating coated at 185~195°C was studied to meet the requirement of the coating temperature of X80 longitudinally welded pipe. The suitable epoxy powders and coating process were determined by evaluating coating properties of varied epoxy powders. The properties of 3LPE, which was coated by using suitable low temperature cured epoxy powder at temperature of 185~195°C, were nearly same to the ones of 3LPE at the normal coating temperature (200~230°C) and meet the requirement of external anti-corrosion properties of X80 longitudinally welded pipe. According to the results, a criteria was provided to CNPC and applied to project of second west-east natural gas transmission pipeline.