A novel, simple self-seeding technique to reduce timing jitter of a GS-DFB laser is proposed. Using this technique, the pulse time jitter is reduced from 5.7 ps to 1.2 ps. The variations of timing jitter under different self-seeding optical power and delay time are measured in the experiment. Both appropriate feedback optical power and delay time are strictly required to suppress the pulse time jitter. When the self-seeding light is injected during turn-on time of GS-DFB laser diode, serious distortion of optical pulses is observed.