Methods, servers, clients, and systems for releasing instant messaging key-value data are provided. A server receives a request packet for pulling key-value data sent from a client during a login. The request packet at least contains a full-amount pulling time-stamp, an increased-amount pulling time-stamp, and a data-altering serial number. The server selects a pre-set data releasing mechanism according to parameters contained in the request packet, to release full amount key-value data to the client or to release increased amount key-value data to the client, or not to release the key-value data, such that, according to a returned result from the server, the client updates local cache data to display to a user.