The invention discloses a method for evaluating vehicle sound quality based on a pupil diameter, and belongs to the technical field of vehicle testing. The method for evaluating the vehicle sound quality based on the pupil diameter is provided aiming at solving the deficiencies that by using a sound quality subjective evaluation method, multi-sample comparison or grading can only be conducted and a specific ratio scale can not be given, and a lot of differences exist in evaluation index selecting of a sound quality objective evaluation method. The method comprises the steps of firstly selecting a sound quality evaluator, collecting a sample to be evaluated, and conducting the sound quality evaluation; then judging whether there is an illuminance-pupil diameter model of the selected evaluator, if there is no model, standard pupil diameter data is collected, and the illuminance-pupil diameter model is generated; if there is a model, the model is utilized to be subjected to sound quality quantization with the sound quality evaluation data. According to the method, a pupil diameter index of the mental load of the evaluator can be reflected through quantization, the deficiency of a ratio scale in the sound quality subjective evaluation method is made up, and the problem of differences of the sound quality objective evaluation index selecting is solved.