The present invention provides a method and a system for improving security of a key device in the information security filed. In order to solve the problem that the security performance of the key device is lower due to the possible tamper of the data needed for encryption and signature in prior art, the present invention provides the method, including steps in which the key device is connected to a computer, then is used to receive the data input by the user through a computer and display the same after a user makes a successful authentication; and to make digital signature or encryption of the data input after the user confirms the content displayed. The above-mentioned system comprises an authentication module, a data receiving module, a display module, a confirmation information receiving module, and a key module. The present invention makes relative display on the key device according to the data input by the user, and provides an input device or generates a random authentication code for confirmation and therefore prevents invalid digital signature or encryption, and improves the security of the key device greatly.