The present invention is a method for implementing instant messaging, including: registering, in a Hook function, a function for registering an instant messaging sub-process in a current running program used for defining a condition for registering the instant messaging sub-process and a process for registering the instant messaging sub-process as a sub-process of the current running program if the condition is satisfied and is used for displaying a instant messaging sub-window in a window of the current running program; and if running an instant messaging program, calling, by the Hook function, the function for registering an instant messaging sub-process in a current running program, if the condition for registering the instant messaging sub-process is satisfied, creating an instant messaging sub-process, registering the sub-process as the sub-process of the current running program, and displaying the instant messaging sub-window in the current running program.