The assessment for a degree of drought has been carried out based on the soil moisture index in Korea. The soil moisture index(Im) was calculated assuming of constant evapotranspiration until wilting point as Im = w_2/w_f·100. The soil moisture content(W2) at the final of a period is obtained from W2 = Pe + W1 - E, here the effective precipitation amount is Pe, evapotranspiration E, and the soil moisture content at the beginning of a period is W1. The filed capacity(Wf), as a mean value of fine sandy loams, was reduced to 92 ㎜/ft when we accept the wilting point and the available soil moisture content of 42 ㎜/ft, respectively. The drought begins in Korea when the soil moisture index drops to less than 50%. The value coincides the isoline of 11 or more consecutive days without measureable precipitation. The soil moisture index frequently drops in the northern part of Youngnam area and Honam area so that both areas are well known as the areas of drought.