An all-fiber double-cladding photonic crystal fiber amplifier is designed and built, and the Yb-doped double-cladding photonic crystal fiber (DC-PCF) is used as the gain fiber. In the experiment, a (6+1)×1 end-pump coupler is fabricated to match the DC-PCF with six multi-mode fibers as pump fibers and ordinary single-mode fiber SMF-28 as the signal fiber. The cladding diameter and the core diameter is 105 μm and 125 μm respectively, and the numerical aperture is 0.22. An end-pump coupler is fabricated by the capillary tube method and directly spliced with DC-PCF. At last, the DC-PCF is spliced with a tapered end-cap. The end-cap is plated with 1000-1100 nm anti-reflective coating film to prevent the entire amplification system from the effect of laser feedback. The designed amplifier is tested with pump light at the wavelength of 976 nm and continuous signal of 2 W at 1064 nm. When the pump power reaches the maximum of 151.83 W, the maximum output power is 108.1 W and the slope efficiency is 72.7%. The output spot is a good fundamental mode spot. It indicates the excellent characteristics of the photonic crystal fiber, which can simultaneously maintain the large mode field and the fundamental mode transmission.