Abstract: In an attempt to assess the relative bioavailability of different dietary manganese sources in broilers, an experiment was conducted using a completely randomized design 2×5 factorial arrangements. A total of 540 healthy one-day-old Avian broilers were assigned randomly into one of ten dietary treatments of 3 replicate cages each with 18 chicks per cage, and fed a basal corn-soybean meal diet (containing 37.66 mg/kg of Mn) added with 0, 45, 90, 130, 180 mg of Mn/kg from a compound amino acid chelate manganese preparation or the basal diet supplemented with 0, 45, 90, 130, 180 mg of Mn/kg from MnSO4·H2O. The feeding experiment lasted for 42 days. At 21 and 42 days of age, the liver, kidney and left tibia tissue samples of the experimental broilers were collected and the Mn concentrations in these tissues were determined by using atomic absorption spectrophotometer. The multiple linear regression fitting between Mn content of different tissues and dietary Mn intake was performed, and the relative bioavailability of compound amino acid chelate manganese to inorganic MnSO4 was calculated with slope ratio method. The results showed that dietary supplementation of Mn obviously elevated the Mn concentration in liver, kidney and tibia in broilers, and the most susceptible response was observed in tibia, exhibiting an obvious dosage effect (P<0.01);compared to Mn concentration in liver and kidney, the Mn content in tibia of broilers aged 21 days was considered as an effective evaluating index for bioavailability of Mn;the relative bioavailability of compound amino acid chelate manganese estimated with slope ratio method was found slightly higher than that of feed grade MnSO4. Our results provide basic data for the rational utilization of organic manganese additive in poultry production.