This study was conducted to investigate the effects of levels and sources of dietary energy on body composition, age of puberty and estrous symptom in replacement gilts. Fifty four Landrace × Yorkshire crossbred gilts with an average initial body weight of (59.0±4.2) kg at (147±3) days of age were randomly allocated to 6 treatments with 9 replicates in each group and 1 gilt in each replicate. Using a 3 × 2 factorial design, three energy levels which were 87.5%, 100% and 112.5% of energy requirement recommended by NRC (1998) were used as experimental treatments, respectively. In each treatment, starch and fat were used as two different energy sources, respectively. Gilts were slaughtered on day 19 of the second estrous cycle. The results showed that gilts in high energy group had higher back fat thickness, lipid content, lean content and lipid/lean compared with those in the other two groups (P<0.05). However, these indices were not significantly different between starch group and fat group (P>0.05). The estrus rate of gilts was increased with the increase of energy level. The age of puberty did not significantly differ among groups with different energy levels (P>0.05), and the age of puberty of gilts in fat group was 21 days earlier than that in starch group (P<0.05). Positive correlations were found between back fat thickness or lipids content and the estrus rate of gilts (R²=0.998, 0.952, P<0.01). Back fat thickness and lipids content of estrous gilts were higher compared with those of anestrous gilts (P<0.01). It was concluded that gilts fed diets containing higher energy level and fat had a better body condition, which stimulated the puberty and estrous symptom in gilts. Meanwhile, back fat thickness and lipid content were correlated with estrus ratio in gilts.