Abstract: By applying sulfanilamide as the marker, the effect of particle size and beeswax content on the bioavailability of beeswax matrix granules was studied.It was found that particle size and beeswax content could independently affect the bioavailability of such granules and the latter played a more important role in increasing the bioavailability.There existed an excellent linear relationship between the cumulative amount of the drug excreted in urine and the time collected in hours. The linearity interrelation coefficients of 0～12 and 0～24 hrs were 0.997～1.000 and 0.985～0.996 respectively. The result revealed that constant sustained release effect was achieved by the type of granules.