A Q-switched Er-doped all-fiber laser, based on a single-walled carbon nanotube saturable absorber (SA) is constructed. The SA with a modulation depth of 8% is prepared using a special chemical-corrosion method. Furthermore, the SA is introduced to an Er-doped all-fiber laser, and Q-switching is obtained successfully. The repetition rate of the Q-switched laser can be tuned continuously from 128 to 278 kHz with pulse widths from 1.92 μs to 488 ns. The maximum output power is 13.1 mW.