Hydroforming is one of the new methods of forming metals, which has been widely welcomed in various industries due to its high speed and low cost of production. This article examines the hydroforming process of the pipe to produce the welded T-Shape. In this research, finite element simulation method was used using Abaqus software, as well as optimization of friction coefficient parameters, mold radius and process time using response surface method and Minitab software. To investigate this process more precisely, the experimental sample with standard dimensions has been simulated by the finite element method and the obtained results have been compared with the existing experimental results. The aim of this research is to achieve the maximum forming of the steel pipe without tearing and to investigate the thickness distribution of the pipe after forming. In this research, the effect of different coefficients of friction on the thickness of the pipe has been investigated and other parameters have been defined and fixed similar to the experimental study. In the following, the optimal values of the process parameters are obtained. The results show that the thickness distribution obtained from the numerical simulation is in acceptable agreement with the experimental results.