Composite microspheres were prepared with hydroxyapatite (HA) and Na-alginate (ALG) via inverse suspension crosslinked method (ISCM). Chloroform/hexane (1 : 2 (volume)) was used as continuous phase, ethyl cellulose (EC) as disperser, mixture of HA powder and ALG solution as dispersed phase, and calcium chloride as crosslinking agent. Morphology of the composite microspheres and HA distribution state were observed by optical n-dcroscope. According to the compositions studied, the sample with 0.2 g of EC gives the best continuous phase. The sample with 25 mL/min of adding speed and 120 r/min of stirring speed gives the best adding and stirring conditions. Two kind of the composite microspheres of 50/50 and 70/30 HA/ALG were prepared via ISCM. They are with specific gravity of 1.06 and 1.15, and water content of 88 and 81%, respectively. The size of the dried microspheres is mainly in the range of 125-425 mu m. (c) 2007 Wiley Periodicals, Inc.