A mode locked Er-doped fiber laser based on a single-wall carbon nanotube saturable absorber is demonstrated.A high quality single-wall carbon nanotubes (SWCNTs) absorber film is fabricated by a polymer composite.The pulse duration is 488 fs with 9.6-nm spectral width at the center of 1564 nm.The repetition rate is 30.4 MHz.The maximum output power is 3 mW.And the single pulse energy is 0.1 nJ.