Social networks have been developed into one of the most important media for information propagation, and it is necessary to disclose how the information disseminates over social networks. In this paper, we explore the spreading mechanism including information stifling and forgetting, establish a spreading model, and elaborate the spreading rules. According to the spreading model, we build the mean field equation, calculate the two equilibriums and the basic reproduction number R0, and prove theoretically the asymptotical stability of the equilibriums. We analyze the effects of stifling mechanism and forgetting mechanism on the information spreading process, and validate the results of theoretical analysis by numerical simulations.