The invention relates to a back-drilling nondestructive testing method for PCBs. A back-drilling testing module is designed next to a PCB production unit, wherein the back-drilling testing module comprises a first testing hole, a second testing hole, a third testing hole, a fourth testing hole, a back-drilling hole, a Top layer, an accuracy testing layer, a drilling layer, a non-drilling layer anda Bottom layer; the Top layer, the accuracy testing layer, the drilling layer, the non-drilling layer and the Bottom layer are sequentially arranged from top to bottom; back-drilling testing is carried out on the back-drilling hole on the accuracy testing layer, the drilling layer and the non-drilling layer through the first testing hole, the second testing hole, the third testing hole and the fourth testing hole separately; the first testing hole and the second testing hole are used for testing the back-drilling accuracy of the accuracy testing layer; the third testing hole is used for carrying out drilling testing of the drilling layer; and the fourth testing hole is used for carrying out non-drilling testing of the non-drilling layer. The back-drilling nondestructive testing method forthe PCBs is suitable for testing of all back-drilling PCBs; the back-drilling depths, the drilling levels and the back-drilling accuracy of the back-drilling PCBs before shipment are tested under thecondition of not affecting the product design of a customer, and the back-drilling quality of each delivered board can be monitored through testing, so that defective products are effectively prevented from flowing to a client; and meanwhile, scrappage of the PCBs caused by slicing is avoided.