The invention relates to a USB Key activation method and system as well as a client. The USB Key activation method comprises the steps of receiving a USB Key application instruction input by a user and collecting a reserved mobile phone number input by the user; sending the reserved mobile phone number and the USB Key application instruction to a server to enable the server to store the reserved mobile phone number; communicating with the USB Key and collecting a verified mobile phone number input by the user, sending the verified mobile phone number to the server to enable the server to send a verification code to the reserved mobile phone number when judging that the reserved mobile phone number is consistent with the verified mobile phone number; and sending the verification code input by the user to the server for verification so as to download a certificate from the server and finish activation of the USB Key after a verification passing result of the server is received. According to the USB Key activation method, a customer can apply for the USB Key on line, activate and enable the USB Key safely, and the customer is accordingly guaranteed to ensure the fund security per se by using the USB Key.