A method for preparing crystalline clopidogrel.bisulfate form I is provided to improve preparation yield of crystalline clopidogrel.bisulfate form I under mild and stable reaction condition, and enhance purity of crystalline clopidogrel.bisulfate form I by preventing contamination of crystalline clopidogrel.bisulfate form II by using a mixed solvent of C3-6 alcoholic and cyclohexane. The crystalline clopidogrel.bisulfate form I represented by the formula(I) is prepared by dissolving clopidogrel.(1R)-(-)-campher-10-sulfonate represented by the formula(III) in organic solvent and neutralizing it with inorganic base to prepare clopidogrel.base represented by the formula(IV), reacting the compound represented by the formula(IV) with sulfuric acid in a mixed solvent of C3-6 lower alcoholic solvent including isopropanol, 2-butanol and 1-hexanol and cyclohexane in a volume ratio of 3:7 to 7:3 at 5-35 deg. C for 4-6 hours, and filtering, cleansing and drying the crystals. Further, a volume of the mixed solvent is 5 to 20 ml based on 1g of the clopidogrel.base.본 발명은 혈소판 응집 차단 효과를 가짐으로써 항혈전제로 유효한 헤테로 사이클린계 약물인 하기 구조식(I)의 결정성 클로피도그렐·황산염(Clopidogrel Bisulfate)의 형태 I (Form I)을 제조하는 신규 방법에 관한 것으로서, 본 발명의 제조 방법에 따르면 일명 결정성 클로피도그렐 · 황산염인 결정성 메틸 (+)-(S)-α-(o-클로로페닐)-6,7-디히드로티에노[3,2-c]피리딘-5(4H) 아세테이트·황산염의 형태 I을 온화한 반응 조건 하에서 고수율 및 고순도로 안정하고도 효율적으로 제조할 수가 있다.(구조식 I)
