We developed a system to measure the absolute frequency of transition of I₂ based on phased locked femto-second laser. The system mainly includes phased locked femto-second laser with repetition frequency of 760 MHz and the 633 nm frequency standard of ECL based on third-harmonic frequency stabilization of iodine saturation absorption. The stabilization of frequency of the femto-second comb generator was achieved by locking both of the repetition frequency(f_r)and the carrier envelope offset frequency(f_ceo)with homemade phase locked circuits and commercial microwave frequency standard. The stability was estimated up to 6.44×10^－13. The absolute frequency was measured by beat frequency between the 633 nm frequency standard locked on the iodine hyperfine transitions and femto-second frequency comb with the help of wavelength meter. Therefore,the transfer from the microwave frequency standard to the optic frequency standard based on the phase locked femto-second laser system has been established,which makes the foundation for the further research.