In this paper,optical waveguides were written by transverse scan of femtosecond laser.Scattered light measurement method was used to measure waveguide transmission loss.In order to improve the transmission performance of optical waveguide,the influence of focusing lens,processing speed and energy of the different numerical aperture on the transmission loss of optical waveguides was analyzed.Experimental results show that,when the numerical aperture of the focusing lens is 0.25,the laser power is 6 mW,processing speed is about 45~60 μm/s,the transmission loss of written optical waveguide is below -0.2 dB/cm.