1. A system for presenting a buddy list on an instant messaging (IM) platform, comprising an IM server and an IM client having a communication connection with the IM server; wherein the IM server is adapted to store at least two of a buddy database, a user information database and a status database; the buddy database is adapted to record a buddy list for each user; the user information database is adapted to record detailed information of each user; the status database is adapted to record a current status of each user; the IM client comprises a grouping and sorting module and a buddy list presenting module; the grouping and sorting module is adapted to group and sort buddies in the buddy list according to one of the buddy list of a user, detailed information of each buddy of the user and a current status of each buddy of the user obtained from the IM server when the IM client receives the user's selection from a first mode based on groups defined by the user, a second mode based on the current statuses of the buddies and a third mode based on the detailed information of the buddies; and the buddy list presenting module, having a communication connection with the grouping and sorting module, is adapted to present the buddy list of the user according to a grouping and sorting result from the grouping and sorting module; wherein the buddy list presenting module supports different presenting manners corresponding respectively to the first mode based on groups defined by the user, the second mode based on the current statuses of the buddies and the third mode based on the detailed information of the buddies, for presenting the buddy list of the user the IM client receiving a user's selection of one from a first presenting manner, a second presenting manner, and a third presenting manner, wherein when the user selects the third presenting manner, automatically grouping by the IM client the buddies in the third grouping manner comprise: grouping buddies logged on within a first period of time into a first group; and grouping buddies logged on within a second period of time into a second group, wherein presenting by the IM client the buddies in the third presenting manner comprises presenting the buddies in the first group and the second group on a screen.