The study investigated the effect of rice particle size on the physicochemical properties of soybean porridge prepared at different pH. Redness, yellowness and viscosity of soybean porridge increased according to the rice particle size. Protein content of soybean porridge was increased 2-fold, compared to that of rice porridges. Total amino acid content of soybean porridge was 1,821.2 mg/100 g and that of rice was 1,719.1 mg/100 g. Lysine and threonine contents of limited amino acid of soybean porridge were increased. Half grain rice soybean porridge exhibited the highest sensory scores. The results indicated that half grain size soybean porridge is preferred, both physicochemically and nutritionally.