The purpose of this study was to investigate the metabolizable energy (ME) and net energy (NE) requirements of Suffolk×Altay crossbred F1 ewes during growing period by feeding test, digestion-metabolism experiment and comparative slaughter test. Forty-five Suffolk×Altay crossbred F1 weaned lambs, at the age of 2.5 months (±3 d) with an average body weight about 19 kg were selected, 15 of them were used for digestion and metabolism experiment, and another 30 lambs were used for comparative slaughter test. In digestion and metabolism experiment, the 15 lamps were fed separately with ad libitum feeding. When the average body weight reached 28 kg, they were randomly divided into three groups (each group had 5 lamps), and fed at three levels:100%, 70% and 40% ad libitum feeding intake, respectively. After a 10-day adjustment, a 6-day digestion and metabolism experiment was carried. After 10 days of ad libitum feeding, the 30 lamps were randomly divided into five groups (each group had 6 lamps) for comparative slaughter test and one group was selected to perform the initial slaughter performance determination. In the remaining four groups of lambs, one group was selected for medium-term slaughter performance determination, and they were slaughtered when their average body weight reached 28 kg. Other three groups were used for late slaughter performance determination, fed at three levels:100%, 70% and 40% ad libitum feeding intake, respectively, and they were slaughtered when their body weight reached 35 kg. The results showed as follows:1) the requirements of net energy (NE_m) and metabolizable energy for maintenance (ME_m) were 0.278 8 and 0.359 6 MJ/(kg W^0.75·d), and the utilization efficiencies of ME for maintenance and gain were 0.78 and 0.44, respectively. 2) The requirements of net energy for gain (NE_g) were 3.38 to 4.68 MJ/d and 4.04 to 5.62 MJ/d when average daily gain was 250 and 300 g/d, respectively. In conclusion, the requirements of ME and NE of 20 to 35 kg Suffolk×Altay crossbred F1 ewes can be counted by factorial models as below:ME=0.359 6 MJ/(kg W^0.75·d)+NE_g/0.44; NE=0.278 8 MJ/(kg W^0.75·d)+NE_g.