The present invention discloses a client function loading method and system, a client, and a server, and falls within the field of communications. The method comprises: acquiring, by a client APP, a function addition request triggered by a user, and sending the function addition request to the server; acquiring, by the server, an installation program for implementing a function indicated by the function addition request; packaging, by the server, the installation program to a plug-in, and sending the plug-in to the client APP; loading, by the client APP, the plug-in to a plug-in environment; and loading, by the client APP, the installation program in the plug-in in the plug-in environment. Compared with the prior art, addition of a client function using the plug-in has the advantages that an APP is prevented from being downloaded and installed to add the client function, thereby reducing the data transmission flow in the addition process of the client function, reducing occupation of a storage space and system processing resources, and improving the user experience.