Abstract：24 first lactation Chinese Holstein Dairy Cattle were used to investigate the effect of diet energy level on reproductive hormones. The energy balance was highly correlated with PRL〔r=－0.9618 (P＜0.01)〕, it was correlated with GH (r=－0.7435) also. The energy balance was negatively correlated with insulin in the phase of negative energy balance; whereas it was positively correlated with insulin in the phase of positive energy balance. The correlation coefficient between energy balance of the seventh week prior to duration of estrus and estradiol is 0.9675(P＜0.01), while the correlation coefficient between energy balance and progesterone is －0.7129. The correlation coefficient between energy balance of the seventh week, and eighth week prior to optimum luteal phase and estradiol are 0.8099 and 0.5775, respectively, the correlation coefficient of progesterone are 0.8263 and 0.6502, respectively,so increasing energy level before calving , it can not only to increase heat detection rate , but also to increase conception rate. In order to increase heat detection rate and conception rate , we can control milk yield within two weeks of postpartum for high producing cows at the same time.