The present invention relates to a method for preparing Clopidogrel and its derivatives. More particularly, the present invention is a method for preparation of (S)-2-Clopidogrel and its derivatives, which are active inhibitors of platelet aggregation, from an optically active (S)-2-chlorophenyl glycine alkyl ester through hydrolysis of racemic 2-chlorophenylglycine alkyl esters using an enzyme. The present invention employs a simple procedure to prepare Clopidogrel and its derivatives. Because no chiral resolving agents are used except for a small amount of enzyme, the cost of preparation can be reduced. In addition, the present invention is suitable for synthesizing highly optical-active Clopidogrel and its derivatives on a large scale by using optically active (S)-2-chlorophenylglycine alkyl ester obtained in high yield as an intermediate, and is also environmentally friendly since no highly toxic reagents are employed.