A method and a system for managing an online shop use an instant messaging system to allow an auxiliary account to log in and manage an online shop of a primary account user. The primary account user creates an online shop in an online shop server, and associates itself with one or more auxiliary accounts in an instant messaging system. Upon authorization by primary account user to allow an auxiliary account to manage the online shop, the system records an authorization relation between the auxiliary account and the primary account. The authorization relation may be recorded in the instant messaging system. Based on the recorded authorization relation, the system allows a user of the authorized auxiliary account to manage the online shop system through the instant messaging system. An instant messaging server serving for this purpose is also disclosed.