In the rail gas pressure welding method, it is necessary to remove the excess weld metal using trimmer and hydraulic pump. The special pump and tool are extremely heavy, and this work requires a great deal of effort. In this study, we investigated a rail gas pressure welding method with a low upset length that can omit the work of removing the excess weld metal to simplify the rail gas pressure welding method. We conducted low upset rail gas pressure welding tests with various pressure patterns and compared the joint performance of the gas pressure welds. This result showed that the low upset rail gas pressure weld used non-constant pressure pattern had the better joint performance than using constant pressure pattern, which is applied high pressure to cause deformation of the interface in the early stage, and then immediately reduced the pressure. Using the non-constant pressure pattern, we conducted various test for evaluating the weld performance using the non-constant pressure pattern with 6mm upset length without pushing out. As a result, the bending strength exceeded the current standard values for rail gas pressure welds, and the bending fatigue strength was over 300 MPa, which is sufficient to withstand repeated train loads.