Abstract: Mastitis of dairy cows,a dairy farm at county of Helan,Ningxia provice,was investigated by dairy herd improvement （DHI） and Somatic cell count （SCC） in the article,its aim was to elucidate the morbidity regularity of Dairy Cattle Mastitis. The results showed that the morbidity rate with clinical mastitis was 3.73 %,the subclinical mastitis was 55.34 %,and the positive rate of mammary region was 22.54 %. With the increase of fetus times and average milk yield and elongation of lactation,the morbidity rate with subclinical mastitis also increased,it was markedly different from that of the prior （P〈0.05）. The morbidity rate of the back mammary regions was higher than that of the forward mammary regions,but there was no significant difference between them （P〉0.05）. In addition,seasons had no significant effect on the incidence of subclinical mastitis（P〉0.05）.