The invention discloses an approximate calculation method for sound pressure level of a loudspeaker mounted on a limited large baffle in axial symmetric simulation analysis of the loudspeaker, and belongs to the field of numerical simulation calculation and loudspeaker design. In order to calculate the sound pressure level of the loudspeaker mounted on the limited large baffle with a 2D axial symmetric simulation calculation method, firstly the baffle is divided into numerous fan-shaped small blocks, secondly the small blocks are approximately merged to relatively few types of blocks according to radius and length standards, thirdly the influence of the multiple types of fan-shaped baffles on a sound field can be calculated with a 2D axial symmetric simulation analysis method, and finally a sound pressure level result under the influence of the whole baffle is obtained. According to the method, the sound pressure level of the loudspeaker mounted on the non axial symmetric baffle is calculated with the 2D axial symmetric simulation method with very small calculation amount, so that simulation calculation conditions are consistent with actual test conditions while the calculation efficiency is greatly improved, and the difference between a simulation calculation result and an actual measurement result is remarkably reduced.