The embodiment of this invention provides a method for classifying and processing data in an instant messaging system, which includes: classifying the data of every service included in the instant messaging system into confidential data and non-confidential data; obtaining and processing the non-confidential data of every service after a first authentication is passed successfully; and obtaining and processing the confidential data of every service after a second authentication is passed successfully. The embodiment of this invention also provides a device for classifying and processing data in an instant messaging system. According to the embodiment of the present invention, the security requirements of the instant messaging system are met, and the user is facilitated to use various services provided by the instant messaging system.