A passively mode-locked fiber laser, whose operating wavelength can be switched based on the single-wall carbon nanotube saturable absorber (SWCNT-SA), is demonstrated. By adjusting the thickness of saturable absorber film to change the intracavity loss, not only stable mode-locked output is obtained, but also the gain profile of the erbium-doped fiber laser is effectively controlled. The experimental results show that the lasers can generate mode-locked pulses with the central wavelength of 1545 nm and 1562 nm, in the thinner and thicker SWCNT-SA, respectively. Additionally if the thickness of SWCNT-SA is appropriately controlled between the thinner and thicker ones, the laser can generate pulses both with central wavelength of 1545 nm and 1562 nm, and the operating wavelength can be switched from one to the other by carefully adjusting the polarization controller. In the process of wavelength switching, the phenomenon of mode-locking is also observed when the two central operating wavelengths simultaneously appear.