This experiment was conducted to investigate effects of application of dairy herd improvement (DHI) system on performance of dairy cows. One hundred and fifty healthy dairy cows with different age, parity and lactation stage were selected in an 8-month (Jun., 2009 to Jan., 2010) experiment. The 1^st month was the period 1, no adjustment was done; period 2 lasted from the 2^nd to the 4^th month, in which the 1^st adjustment was carried out; period 3 lasted from the 5^th to the 7^th month, in which the 2^nd adjustment was carried out; the 8^th month was period 4, which was the observation period after adjustment. The adjustments of diet and managements were determined based on the climatic condition in Bayenaoer, Inner Mongolia and data from the DHI report during the experimental period. Milk yield was recorded. 305 d milk yield and 305 d matured equivalency were calculated, peak daily milk yield and its time were predicted by DHI software, and milk sample was collected once a month for the determination of the ratio of fat to protein in milk. The results showed that application of the DHI system significantly increased 305 d milk yield and 305 d matured equivalency (P<0.05), significantly increased peak daily milk yield and shorten its time (P<0.05), and the ratio of fat to protein in milk was improved. The results indicate that under the climatic condition in Bayenaoer, Inner Mongolia, application of the DHI system can improve performance of dairy cows.