Butt fusion welding is one of the important methods of joining polyethylene pipes. Despite the widespread use of this method, a comprehensive and complete study has not been done yet. In this article, after designing the experiments, experimental tests were carried out in different conditions and the tensile strength of their welds was obtained through the tensile test. Then, based on the experimental results, the effect of welding parameters such as temperature, pressure and time of the welding process on the strength of the weld was investigated. For better analysis of the results, finite element simulation was also used in Abaqus software. Then, using response surface methodology, welding parameters were studied and optimized. The optimization model shows that the maximum tensile strength is obtained in the welding conditions of welding temperature 190 °C, pressure 23.33 bar and welding time 240 seconds, which is equal to 10.127 MPa. The results of practical tests for the optimal point confirmed the results of the model and its error was 3.3%. The strength obtained for welding in optimal conditions was about 2% higher than the strength of the base material.