An all-fiber Q-switched laser including a laser resonant cavity and a loop optical system is provided. The loop optical system is disposed inside the laser resonant cavity, and the all-fiber Q-switched laser generates a pulsed laser through the loop optical system. The loop optical system includes a plurality of wavelength-division elements and a saturable absorber. One of the wavelength-division elements is coupled with another one of the wavelength-division elements through corresponding first connecting fibers. Two ends of the saturable absorber are respectively coupled to second connecting fibers of the wavelength-division elements, wherein the saturable absorber and the two wavelength-division elements form a loop such that an auxiliary unsaturated light source can be transmitted in the loop.