Disclosed is an ultrasonic welding method. The method comprises: checking whether ultrasonic heights between each pair of pre-welded members are the same; selecting members having the same ultrasonic height, so as to choose an ultrasonic apparatus with a matching frequency according to the ultrasonic heights of each pair of members; for members having different ultrasonic heights, checking whether partial welding surfaces having the same ultrasonic height and meeting a fixing requirement are present; if the partial welding surfaces having the same ultrasonic height exist, choosing an ultrasonic apparatus with a matching frequency according to the ultrasonic height of the partial welding surfaces; if the partial welding surfaces having the same ultrasonic height do not exist, checking whether curvature of the welding surfaces is less than a first set value; if so, choosing an ultrasonic apparatus with a matching frequency according to the maximum ultrasonic height of the welding surfaces; and on the basis of an assembly sequence, performing ultrasonic welding according to the ultrasonic apparatuses with matching frequencies corresponding to each pair of members. The above method of the present invention is suitable for ultrasonic welding of multiple workpieces and different welding surfaces.