Objective:To prepare rh-endostatin loaded poly(lactic-co-glycolic acid)(PLGA)microspheres and to evaluate their release behavior in vitro.Methods: Rh-endostatin PLGA microspheres were prepared by W/O/W process.The content and in vitro cumulative release was determined by a HPLC method.Results: The prepared microspheres were well-shaped, with a mean diameter of 122.7 μm.The drug loading and encapsulation efficiency were 1.28% and 38.65%, respectively.The rh-Endo solution (250 μg/ml) showed good stability after placed at 4℃ and 25℃ for 108 h.The cumulative in vitro release was up to 67.37% in 28 days.Conclusion: The rh-Endo can be encapsulated in microspheres to yield sustained release using biodegradable polymers PLGA as the carrier material.