Microencapsulated acetaminophen granule was prepared in a fluid bed granulator, using ethylcellulose as coating material. We studied the effect of two important control factors, inlet air temperature and liquid flow rate. To evaluate various acetaminophen granules which were prepared by different conditions (inlet air temperature; 40℃, 50℃, 60℃, liquid flow rate; 18㎖, 36㎖, 54㎖, 72㎖/min), we used scanning electron microscope, dissolution tester, sieve analyzer and bulk densitometer. From above results, it was found that at inlet air temperature 50℃ and liquid flow rate 54 ㎖/min we could obtain a smooth and continuous granule surface, a narrower granule size distribution and 90% dissolution time 30-40min.