Abstract: [Objective] The problem of fecal pollution in large-scale dairy farms has become increasingly prominent and has become an important factor restricting the sustainable development of dairy farming. Using Recycled Manure Solids（RMS）for cows is one of the effective ways to realize the harmless and resource utilization of cow dung. [Method] The solid cow dung with different dry matter contents（30%~35%, 35%~40%,40%~50%） was stacked and fermented. By comparing the temperature of different dry matter cow dung stacks,the change trend of harmful microorganisms,and the comparison of physical and chemical properties after stacking,the optimal safe preparation process of RMS materials was established,and its impact on the incidence rate of mastitis was evaluated. [Result] 35%~40% dry matter content of cow dung was piled into a trapezoidal fermentation stack with a height of 1.2 m,a bottom width of 1.5~2.0 m,a top width of 1.2 m,and a length of 20~30 m. After the 4th day of fermentation,the temperature of the surface and middle layers of the fermentation stack reached above 60 ℃.The fermentation temperature above 60 ℃ for 24 hours can kill 100% of the pathogenic microorganisms of mastitis.After the fermented cow dung is dried to make its dry matter content reach 45%~50%,mixed with 0.1%~0.2% quicklime can be used as bedding material. [Conclusion] After 35%~40% dry matter content of cow dung is fermented,and the fermentation temperature is above 60 ℃ for 24 hours,it can kill 100% of the pathogenic microorganism of mastitis. After fermentation,the dry matter reaches 45%~50% after drying,mixed with 0.1%~0.2% quicklime can be used as bedding material. The preparation time of RMS material is the shortest, and the use effect is the best.

Key words: Recycled Manure Solids（RMS）, safe preparation, dry matter, microorganism, mastitis