A home-made Er: fiber optical frequency comb aimed at measurement of frequency of D1 line in Li atoms was demonstrated.The system includes Femtosecond laser, frep and fceo detection and control, Spectral broaden and Beat unit. Femtosecond laser is a home-made nonlinear-polarization-rotation mode-locked laser, oscillating at around 1 572 nm with a repetition rate of 196.5 MHz. The fceo detection is accomplished by using the f-2f beating method, the signal-to-noise ratio of fceo about 40 dB with 300 kHz. fceo controlled by changing the pump current and its in-loop frequency instability, evaluated by the Allan deviation, is approximately 3.74×10-18/τ1/2;frep controlled by changing the cavity length of femtosecond laser, its in-loop frequency instability is approximately 1.75×10-13/τ1/2. Optical spectrum is broadened and multipliered from infrared 1 520-1 607 nm to 671 nm by using highly nonlinear fiber and MgO: Periodically poled lithium niobate. Finally, obtaining the beat signal between sigle-frequency laser and optical comb about 60 dB with 1 Hz.