A new method for measurement of propagation loss optical wave-guide is particularly introduced, which is called matching liquid measurement. By inserting the waveguide into the matching liquid,whose refractive index is higher than the one of waveguide,the radiation intensity along the waveguide is obtained. The attenuate curve can be imitated. Compared with the traditional method,this method can be used to measure the waveguide repeatedly,especially for the measurment of optical waveguide whose propagation loss is lower than 0.1 dB/cm.