The embodiment of the invention provides a method and a device for creating backlogs in an instant communication system. The method comprises the following steps of distributing a backlog box with a unique storage address to a registered user in the instant communication system; displaying the backlog box at the preset position and the main window of the instant communication system; if an instruction of creating backlogs triggered by the user through the displayed backlog box is received, creating the backlogs in the backlog box according to the specific content of the backlogs input by the user, reminding time selected by the user, and other colleague users who are about to be notified of the created backlogs or be distributed with the created backlogs, wherein the backlogs include a text, a record, a picture, a video, segmentation, line break, a separator, a serial number, and/or a to-do list. Through distributing the backlog box with the unique storage address to the registered user in the instant communication system, the backlogs can be created in the instant communication system, and a to-do message for creating a rich text content is supported.