A making method of a key of a mobile device mainly comprises the following: a system on-line step: a preset server end is connected by means of a mobile device; an identity certification step: personal data is input through the mobile device to verify the identity of a user; a data uploading step: the mobile device sends the specific recognition information of the device to the server end, thereby providing a making certification key for the server end; a download making step: the server end makes the specific recognition information of the mobile device into the certification key and sends the key to the mobile device. By means of the steps, a user can combine the needed certification key with the mobile device to provide a certification mode with both safety and convenience.