7 sorts of modal/cotton blended yarns were prepared with different blending ratio. This article studies the relationship between the wear comfort performance and blending ratio. By the analysis of the moisture adsorption, moisture-air permeability properties, the optimum blended ratio of the modal/cotton blended fabric is determined. The results indicated that the excellent wearing comfort of modal/cotton could be adjusted by changing the compositions. The results indicated that the properties of the modal/cotton fabric could be adjusted by changing the compositions, which can be seen the development of good underwear fabric fiber raw materials.