The purpose of this study is to prevent the generation of crystal in Sufu and provide foundation for its prevention in future.We took grey Sufu as the main study object and analyzed the differences of related indicators among green curd Sufu with crystal in different period of late fermentation.Then we did a model test based on different effectors that influence the production of crystal in Sufu.We found that along with the prolongation of the later fermentation,the concentration of NH 4 +and pH value of Sufu both were increasing.The content of P was increasing at first and decreasing later.The content of Mg was decreasing.The concentration of NH 4 +and pH value both had a great influence on the generation of MgNH 4 PO 4 ·6H 2 O.But salinity and the content of alcohol had little effect.Therefore,we could conclude that the generation of large amounts of crystal might be caused by the increasing concentration of NH 4 +which produced during long-term later fermentation period.Low salinity and high alcohol content would promote the generation of the crystal.