The Tm3+-doped fiber is the key of Tm3+-doped fiber laser, which has broad application prospects. In this paper, the silica-based Tm3+-doped fiber preform is manufactured by gas-solution co-doping method in MCVD(modified chemical vapour deposition) and the Tm3+-doped double-cladding fiber is also achieved, the core and cladding diameters of which are 10 μm and 125 μm respectively. We prepare the Tm3+ all-fiber laser using the Tm3+-doped fiber and when the laser is pumped by a 793 nm laser diode, the center wavelength is 2002 nm, maximum output is 31.7 W, and the slope efficiency of the fiber is 59.32%.