An information sharing method, server, and system are provided. The information sharing server includes: a re-sharing requesting unit, adapted to send a re-sharing setting request for allowing re-sharing after receiving a setting instruction for allowing information re-sharing from a sharing provider; a re-sharing setting unit, adapted to receive the re-sharing setting request for allowing re-sharing from the re-sharing requesting unit, and set target shared information to a state in which a sharing receiver is allowed to re-share the information; a re-sharing indicating unit, adapted to send a re-sharing request after receiving the re-sharing requesting instruction; and a re-sharing unit, adapted to receive the re-sharing request directed to the target shared information from the re-sharing indicating unit, and set the target shared information to a sharing state. Thus, a sound and flexible information sharing mechanism is provided.