Abstract: In order to address the welding quality issues caused by inconsistent indoor and on-site construction environment during the hot melt welding of polyethylene pipes, the finite element method in Ansys software was employed to analyze the influence of different environment on temperature uniformity and melt layer thickness, and to evaluate the welding process. Based on the melt layer thickness, an optimization model for the welding process was established and the optimized welding process parameters were validated through tensile experiments. The results showed that under certain environmental conditions, the pipe temperature gradually approached the ambient temperature as the axial distance increased. The uniformity of temperature at the welding end decreased first and then gradually increased with an increase in cooling time, reaching a minimum at around 200 seconds. The melt layer thickness gradually decreased with a decrease in environmental temperature and an increase in wind speed, with a maximum reduction of 25%. The difference between the tensile strength of the optimized sample and that of the indoor standard welding process was within 5% and met the standard welding quality requirements.