Abstract: OBJECTIVE To prepare sirolimus micro-particles by supercritical anti-solvent fluidized bed(SASFB) coating technology, and to investigate the particle morphology and dissolution in vitro.METHODS Lactose was selected as carrier, and three process parameters including temperature, pressure and drug concentration were optimized by orthogonal experimental design.RESULTS The process optimization experiment demonstrated that drug concentration had the greatest effect on the coating efficiency of sirolimus, followed by pressure and temperature. The optimal conditions were temperature 45℃, pressure 8 MPa, drug concentration 1 mg·mL^-1. The sirolimus particles prepared by SASFB were evenly dispersed on the surface of the carrier, the dissolution rate were 2.29 and 5.04 times of the supercritical anti-solvent sample and sirolimus active pharmaceutical ingredient in 20 min, and the coating efficiency could reach 74.1%.CONCLUSION SASFB is a new type of pharmaceutical preparation technology for preparing micron particles of sirolimus in one step.