Objective This experiment was to evaluate the effect of different inclusion levels and adaptation periods on digestible energy (DE) and the apparent total tract digestibility (ATTD) of chemical constituents in diets supplemented with wheat bran. Methods Thirty-six crossbred barrows with an initial body weight (BW) of 85.0 ± 2.1 kg were allotted to 6 diets in a completely randomized block design with 6 pigs per diet. Diets included a corn-soybean basal diet and 5 additional diets which formulated by replacing corn and soybean meal in control diet with 15, 25, 35, 45, or 55% wheat bran. The experiment lasted for 34 d, and feces were collected from d 8 to 13, 15 to 20, 22 to 27, and 29 to 34 respectively. Results The results showed that no interaction effects between inclusion level and adaptation period on the concentration of DE and the ATTD of GE and CP in wheat bran were observed. The DE value and ATTD of GE in wheat bran decreased (p<0.05) significantly as the inclusion level of wheat bran increased, but no difference in the ATTD of CP was observed. The ATTD of CP in wheat bran increased (p<0.10) significantly as prolonging the adaptation period for pigs. In addition, the concentration of DE and the ATTD of GE in wheat bran decreased linearly (p<0.05) when fed to pigs as increasing inclusion level of wheat bran or adaptation period of diets. Conclusion Wheat bran showed a negative effect on the concentration of DE and ATTD of GE and CP as the inclusion level increased. The longer adaptation period can increase gradually the DE value and ATTD of GE and CP in wheat bran, and at least 14-21 d of adaptation might be recommended for growing-finishing pigs fed the high-fiber diets with wheat bran.