The invention discloses an online game client side resource downloading method, comprising the following steps that: step 1, the online game client resource is divided into a minimum client side and a residual resource; the client side downloads and installs the minimum client; step 2, the client side starts an online game, in a process of playing the online game, the client side senses bandwidth and downloads the residual resource through idle bandwidth; step 3, after ending the online game, the client side downloads an updating program to reside in the client, and continues to downloads the residual resource through the idle bandwidths. The method can simplify and facilitate the downloading process of clients, and can shorten time of deployment process of a game client side, so that game players still can quickly enter into the game when the client side resource is larger, and also can download the resource in the process of playing the game, thereby increasing interest of the clients to the online game, preventing client loss and attracting new clients.