The setting process of the Alkali Activated Cement (AAC) generally is too rapid to be handled at the building site;to prolong the setting time of this type of cement is a key issue of its application.This paper reports a new invented approach to regulate alkali activated slag-fly ash activated (AASFA).A special mineral admixture was prepared and its parameters are optimized.Results indicate that this admixture has strong effect to prolong the setting time, it prolongs the initial setting time from 50 to 320 min and retards the final setting time from 180 to 500 minutes, the adding of this special admixture also enhances the strength of the AAS very significantly, the hydration products and the early hydration process of this new type of cement is investigated, the gel Ettringite (AFt) in this cement delay the rapid hydration of ASSFA and nearly no crystal hydration product is found in the hardened paste of this cement, after significant retardation of setting time the peaks of exothermal curve of the hydration did delay but appeared earlier.This type of agent can service as a retarder of AAC not only as gypsum in Portland cement and but also chemical retarding agents in the Portland cement and concrete.