This study was conducted to investigate the effects of stocking density, sex and dietary metabolizable energy (ME) level in a high-protein (23% in early phase and 21% in later phase) diet on growth performance and leg health of broiler chickens. According a 2 (sex)×2 (stocking density)×3 (dietary ME level) three-factor completely randomized design, 1 872 male and 2 160 female 1-day-old Ross 308 broiler chickens were allotted into 12 groups with 8 replicates per group. Two stocking densities were designed in this experiment:42[high stocking densities (HSD), 16 males/m² or 18 females/m²] and 26 kg market weight/m²[low stocking densities (LSD), 10 males/m² or 12 females/m²], respectively. The experiment contained early phase (1 to 21 days of age) and later phase (22 to 35 days of age), and dietary ME levels divided into high, middle and low levels. The ME levels of high ME (HME) level diet were 12.81 and 13.23 MJ/kg, the ME levels of middle ME (MME) level diet were 12.18 and 12.60 MJ/kg, and the ME levels of low ME (LME) level diet were 11.55 and 11.97 MJ/kg in early phase and later phase, respectively. The results showed as follows:1) stocking density and dietary ME level had significant interactions on average daily gain (ADG) and the ratio of feed to gain (F/G) of broiler chickens (P<0.05). Increase range of ADG and decrease range of F/G from 1 to 21 days of age in HSD group were lower than those in LSD group with the increase of dietary ME level, however, the results were the opposite from 22 to 35 days of age. Sex and stocking density had significant interaction on average daily feed intake (ADFI) of broiler chickens (P<0.05). Decrease range of ADFI of male broilers was higher than that of female broilers with the increase of stocking density. 2) HSD significantly decreased breast muscle yield of broiler chickens (P<0.01), and breast muscle yield and abdominal fat percentage of female broilers were significantly higher than those of male broilers (P<0.05). Stocking density and dietary ME level had significant interactions on thigh muscle yield of broiler chickens (P<0.05). Thigh muscle yield of broiler chickens in LSD group was decreased, but there was no change in HSD group with the increase of dietary ME level. 3) Dietary HME level significantly decreased footpad burn score of broiler chickens (P<0.01), gait score and footpad burn score of male broilers were significantly higher than thaose of female broilers (P<0.05), and litter moisture content of male broilers was significantly lower than that of female broilers (P<0.05). Stocking density and dietary ME level had significant interaction on footpad burn score of broiler chickens (P<0.05). Decrease range of footpad burn score in HSD group was higher than that of LSD group. In conclusion, HSD decreases ADG and increases F/G of broiler chickens, male broilers need more space than the female before 35 days of age, increasing ME level in the high-protein diet can alleviate the negative effects of HSD on growth performance and footpad health.