Abstract: Disclosed are an acid-resistant pharmaceutical composition including tamsulosin hydrochloride, and a method of preparing the same. The pharmaceutical composition is formulated into tablets by preparing core beads including tamsulosin hydrochloride as an active ingredient, coating the core beads with an entering coating solution including a specific amount of plasticizer, adding a post mixture portion including a buffer to adjust density and a lubricant to the enteric-coated core beads, and performing tableting. The enteric coating layer is not broken during the tableting process. Thus, the acid resistance of the pharmaceutical composition is maintained. The pharmaceutical composition can be easily formulated into tablets, ensures good uniformity of dosage unit, lowers dissolution rate of tamsulosin hydrochloride, has good acid resistance, and is stable not to exhibit signification decomposition of tamsulosin hydrochloride.