Abstract: OBJECTIVE To prepare and identify sustained-release of isoniazid solid dispersion(SD) and evaluate its in vitro dissolution profile. METHODS The isoniazid SD was prepared by using water-insoluble polymer ethyl cellulose (EC) as carrier. X-ray diffraction, differential scanning calotimetery (DSC) and infrared spectroscopy (IR) were used to evaluate the dispersing state of isoniazid in SD and in vitro dissolution of isoniazid SD was performed. RESULTS X-ray diffraction analysis showed that the isoniazid was existed in both molecuar and micro-crystal form. DSC curve indicated that there was no isoniazid crystal in the SD. IR spectrum showed that there was no chemical reaction of isoniazid with the EC. The test for dissolution rate showed a better releasing in SD. CONCLUSION The SD can disperse the isoniazid to get sustained-release effect.