Variation of free swell index of powder and granular bentonite in distilled water were reviewed. For this, four types of additives is used such as starch (SC), sodium carboxy-methyl cellulose (SCMC), polyvinyl alcohol (PVA-Iand PVA-II), super absorbent polymer (SAP). For PVA-I and PVA-II, free swell index increased with 0.2 g addition. However, SC showed a little increase and SCMC showed higher increase. Especially for SAP addition, powder bentonite has larger free swell index to compare with granular bentonite. The sequence of contribution to free swell index of bentonite in descending order is SAP, SCMC, PVA-II, PVA-I, and SC.