Tibet kefir（TK） is a kind of yoghurt fermented by Tibet kefir grains （TKG）， which consist of lactic acid bacteria， yeasts and acetic acid bacteria. TK is traditional fermented milk in pastoral area in China with the aroma of milk and bouquet， which also has foaming property and probiotic function. Therefore， it has a reputation as Champagne yoghurt. However， TK has not been industrialized because of the complicated microbial composition and the uncontrollable fermentation. Artificial TK starter with specific microbial composition and controlled fermentation need to be developed. In this paper， three construction hypotheses of TKG were deduced and they were biofilm hypothesis， aggregation hypothesis and symbiosis hypothesis. Besides， the possible reasons for the failure of artificial grain construction were analyzed， together with the assumed hypotheses， which could shed light on the formation mechanism and be conducive to artificial construction of TKG.