Moisture transmission rate in fabric and humidity of diffusion layer over the fabric have been measured by weighing and humidity gradient procedure based on the cup method, respectively. The diffusion's law of moisture transmission was applied to the air layer in the cup, the space in the fabric, and the air layer over the fabric. The transmission coefficient of moisture in the fabric was calculated by solving the simultaneous equations. It was about 2_??_15×10-3m2/h, and the values correspond to 2_??_14% of the diffusion coefficient of water vapor in air. The transmission resistance and convection coefficient of moisture on the surface of fabric were estimated to 5_??_8m/h and 11_??_20×10-2h/m, respectively. The transmission resistance of moisture in fabric was about 10_??_30% of the total transmission resistance of moisture of the experimental system.