Abstract: Dairy herd improvement （DHI） could provide accurate and reliable information for pasture，which could be helpful for the management of herds.This paper analyzed the indicators of DHI，and based on DHI data from February 2012 to December 2012 of a dairy farm in South China， this paper performed trend analysis for milk fat rate，milk protein rate，milk lactose rate，the number of somatic cell and daily milk yield and make correlation analysis of factors of daily milk yield by gray relational model.The results showed that the milk production from February to October was declined，which showed that the rearing environment of herds was poor.The milk lactose rate，milk protein rate and milk fat rate were increased，which showed that the diet structure was reasonable and the dietary dry matter was adequate.The somatic cell count was less than 500000/mL，which showed that the incidence of mastitis was lower and the herds were in good health. The number of somatic cell was also the most influential factor of the daily milk yield，and there was a very strong negative correlation among them.Therefore，strengthening the management of cattle rearing environment，improving the level of breeding cattle breeding，adjusting the dietary nutrition structure and doing mastitis detection and prevention were very important for dairy managers.

Key words: dairy herd improvement; cow; gray relation