An implementation method for increasing the number of certificates supported by a PIV application, the method comprising: a virtual machine of a key device is powered on; a data endpoint address is set to be an endpoint address of a CCID interface that receives instruction data; according to the instruction data, APDU data used for the authentication of a PIV application is obtained; and the APDU data used for the authentication of the PIV application is sent to a PIV application of the key device; the PIV application calls an API interface to obtain a CCID interface number, obtains a PIV device certificate number according to a general device certificate number in the APDU data used for the authentication of the PIV application and the CCID interface number, obtains a PIV certificate according to the PIV device certificate number, and operates according to the PIV certificate to obtain operation results; and the virtual machine returns the operation results to an upper computer according to the data endpoint address. The method further comprises: when a USB interrupt is triggered, a USB interrupt process is executed. The described method overcomes the limitation of the number of certificates supported by a PIV application while simplifying operations.