Abstract: In order to study the effects of different relative humidity on the quality of yak mold cheese during ripening,and determine the optimal relative humidity and ripening time in the ripening process,the yak mold cheese was taken as the experimental materials and was ripened in the relative humidity of 30%,50%,70%. The changes of sensory quality,texture,pH value,nutrient content,the decomposition indexes of protein and fat and the changes of volative flavor compounds were measured during the ripening process. The results showed that the sensory score of the cheese was highest and the texture index was better when the ripening relative humidity was 50% and fermented for 6 days. Meanwhile,with the extension of ripening time,moisture content protein content and fat content in the three experimental groups all presented a downward trend,nevertheless,the ash content showed an upward trend,while the pH value decreased first and then remained unchanged or increased. Furthermore,except for 0 and 8 days of ripening,at the same maturity time,the relative moisture content of 30% was significantly lower than the other two groups(P<0.05). The ash content,protein content and fat content did not change significantly. The pH value of 50% relative humidity decreased the fastest. Meanwhile,the content of soluble nitrogen at pH4.6 or 12% trichloroacetic acid soluble nitrogen,thiobarbituric acid value,acid value increased gradually during cheese ripening,and the highest value was obtained at relative humidity of 50%. The detection of volatile flavor substances in yak mold cheese indicated that the flavor content of the cheese was higher when the relative humidity was 50%,and the cheese was ripened to the 6th day. Therefore,the quality of yak mold cheese was the best when the relative humidity was 50% and the ripening time was 6 days.