We theoretically demonstrate a compact all-dielectric metasurface fiber-tip lens composed of sub-wavelength amorphous silicon on the end face of a multimode fiber. The full 2π phase control was realized by varying the widths of resonant units. The tunable focal length is achieved by using the thermal-optic effect of amorphous silicon. The focal length increases from 309 μm to 407 μm when the temperature changes by 300 K. The temperature controlled all-fiber integrated lens is compact and with high efficiency and provides an excellent platform of a fiber-tip lab. Meanwhile, the proposed fiber lens does not have any structural changes during dynamic tuning, which improves the durability and repeatability of the devices.