Abstract: AIM　To increase the bioavailability of melatonin (MT), MT gelatin microspheres (MT-GMS) for intranasal administration were prepared. METHODS　MT-GMS were prepared using emulsifying-cross linking technique. Orthogonal tests were used to optimize the preparation conditions. The residence time of technetium-99m (^99mTc) labeled gelatin microspheres (GMS) in the nasal cavity of rabbits as compared to gelatin solution, was investigated using gamma scintigraphy. Furthermore the bioavailability in rabbits was examined for evaluating MT-GMS. RESULTS　The mean diameter of MT-GMS was 50.2 μm, the particle size focused on 30～70 μm. The drug content was 13.48%. The release profile in vitro showed sustained effect. The residence time of GMS in the nasal cavity of rabbits was longer than that of gelatin solution. After intranasal administration in rabbits, the bioavailability of MT-GMS was 87.47% as compared to vein injection, while the bioavailability of MT solution was 69.72%. CONCLUSION　MT-GMS prepared could meet the needs of intranasal administration, and could increase the bioavailability of MT.