In this study, copolymers of the ratio 70:30, 80:20, and 90:10 of lactide and glycolide for drug carriers of DDS were synthesized from lactic and glycolic acids. Copolymers microspheres and copolymers microspheres containing clonazepam prepared by dialysis method. Then sizes of microspheres containing drug rather uniformed more or less in 0.5-1.5㎛ and their sizes are bigger than diameters(0.3-0.5㎛) of copolymers microspheres. The linearly release time according to the kinds of microspheres was delayed in the order of DL-PLG (70:30) > DL-PLG(80:20) > DL-PLG(90:10). In short, the formulation allows polymeric micelles to suppress the burst effect of the drug release mechanism, which led to the controlled release pattern and micelles.