The present invention relates to a fat-free soymilk composition using isolated soy protein and a method for preparing the fat-free soymilk composition using isolated soy protein, and more specifically, to a fat-free soymilk composition using isolated soy protein, the composition comprising isolated soy protein, micro-ground grain powder, sweetener, stabilizer, emulsifier and purified water, and a method for preparing the fat-free soymilk composition using isolated soy protein. A method for preparing a fat-free soymilk composition using isolated soy protein according to the present invention comprises: a step (a) of mixing 4 to 10 percentages by weight of isolated soy protein and 0.5 to 5 percentages by weight of grain powder with purified water having a temperature of 40 to 80 °C at a ratio of 1:3 to 1:13, and primarily homogenizing the mixture at a pressure of 200 to 300 kg/cm^2 to prepare a stable emulsion a step (b) of adding 0.01 to 0.2 percentage by weight of a stabilizer and 1 to 10 percentages by weight of dextrin as a carbohydrate supply source to the emulsion, secondly homogenizing the mixture at a pressure of 200 to 300 kg/cm^2, and finely grinding resulting particles to obtain a liquid phase homogenized solution having increased settling and separation stabilities and a step (c) of instantly sterilizing the homogenized solution at an ultra-high temperature of 130 to 140 °C for 20 to 50 seconds, cooling the instantly sterilized homogenized solution to a temperature of 10 to 20 °C, charging the cooled homogenized solution into a sterilized container, and sealing the container. The method further comprises a step of packing the sealed container containing the homogenized solution into a separate container, and secondly sterilizing the container containing the homogenized solution-contained container to a temperature of 120~135°C. The total weight of the respective ingredients is 100 percentages by weight. The present invention provides a soybean
