Gembili (Dioscorea esculenta) is a tuber-producing plant containing 14.63% inulin, a Water-Soluble Polysaccharide (WSP). This study aims to determine the optimum point of material to solvent ratio and Microwave-Assisted Extraction (MAE) time needed to extract gembili WSP, and determine the WSP's characteristics produced. The optimization process uses the Response Surface Methodology-Central Composite Design (RSM-CCD) with Design Expert 7.0 software. The material to solvent ratio's minimum and maximum points are 1:25 g/L and 1:45 g/L, while the minimum and maximum points of extraction time are 20 minutes and 40 minutes. This study observed 13 experimental combinations and responses from gembili WSP yield, WSP powder inulin levels, and WSP solubility. The results showed that the optimum conditions of material to solvent were at a 1:33.81 g/mL ratio, and the extraction time was 29.26 minutes. This optimum condition resulted in 32.42% WSP yield, 40.8% inulin content in WSP powder, 26.98% WSP solubility, 12.24% WSP water content, and 49.3 cp WSP viscosity. These results indicate that extraction using a microwave can increase WSP's rich inulin yield from gembili tubers. Keywords: gembili, inulin, microwave, optimization, Water-Soluble Polysaccharides