The invention provides a steel-aluminium transition joint T-shaped bilateral space welding process numerical simulation calculation method, and belongs to the field of welding numerical simulation. The steel-aluminium transition joint T-shaped bilateral space welding process numerical simulation calculation method includes the steps that a three-dimensional or two-dimensional thermal-mechanical coupling calculation model of a steel-aluminium transition joint welding process is established; initial conditions and boundary conditions of the welding model are set; a heat source equation correction method of a T-shaped joint with welding angles is determined; a T-shaped bilateral space welding heat source subprogram is established; a task is submitted and solved, and then pose-processing and analysis are carried out. The steel-aluminium transition joint T-shaped bilateral space welding process numerical simulation calculation method has the advantages of being capable of achieving the purpose that numerical simulation calculation of a temperature field and numerical simulation calculation of a stress field can be conducted synchronously in a three-dimensional or two-dimensional T-shaped joint bilateral space welding process. By establishing a geometric structure of an actual steel-aluminium transition joint and correctly setting a bilateral space welding heat source model with angles, the influences of different welding line energies and bilateral space welding durations on a steel-aluminium interface highest temperature can be predicted, and choices for practical welding process parameters and time intervals of bilateral welding operation are guided.