A new method for side-pumping double-cladding fiber is researched. A column of 3 mm length is cut off from D-shape double-cladding fiber which has a transverse sectional dimension of 350 μm×400 μm. Then the column-fiber coupler is formed by gluing the column onto the side of inner cladding. The pumping light is coupled into the inner cladding from the end of column. When the output power is 1.3 W from the forward end of the coupler, the optimum efficiency is 85%. This method suits for pumping the fiber laser and amplifier of several watts output power.