Abstract: Red phosphorus microencapsulation flame retardant was prepared by Supercritical Fluid-Rapid Expansion of Supercritical Solutions (SCF-RESS)，using a self-made special nozzle. The influences of temperature of the nozzle，temperature in the high-pressure kettle，molar flux of the red phosphorus particles and pressure in the kettle on coating effect were discussed. The results showed that red phosphorus microencapsulation particles were prepared when both temperature in the kettle and temperature of the nozzle were 120 ℃，molar flux of red phosphorus particles was 1.5 g/min，and pressure in kettle was more than 16 MPa.