The invention discloses an approximate calculation method for a harmonic distortion of an axisymmetric loudspeaker on a finite baffle, and belongs to the fields of data simulating calculations and loudspeaker designs. The method comprises the following steps: firstly, calculating a harmonic distortion feature of the axisymmetric loudspeaker in the presence of an infinite baffle or in the absence of the baffle, and a sound pressure level frequency response of a frequency point with a frequency being 1-5 times of a fundamental frequency; secondly, approximately assuming that one large baffle is spliced by a plurality of small fan-shaped baffles, acquiring sound pressures under the influences of the fan-shaped baffles with a 2D axisymmetric simulated analysis method, and combining the acquired sound pressures to obtain a sound pressure level frequency response feature under a baffle condition needing to be analyzed; and lastly, calculating a total harmonic distortion (THD) and second to fifth harmonic distortions (HD2-HD5) of the axisymmetric loudspeaker under the condition of the finite baffle according to a formula. Through adoption of the method, the harmonic distortion features of various axisymmetric loudspeakers arranged on various finite baffles can be calculated rapidly and accurately.