As a splitter, the common fiber coupler has a low insert loss, while as a combiner it exhibits high loss. In order to obtain the combining beams with low insert loss, a new configuration coupler is presented, which is consituted with a single-mode fiber and a multimode fiber. The working principle is theoretically analyzed by the coupling wave equation and the coupling procedure is simulated by the computer. The coupler was made with a single-mode fiber and a multimode fiber by fused-taper technology. The result agreed well with the simulating drawing. The combining of two beams is realized. The coupling ratio of each arm is more than 90%. As a combiner, with low insert loss, this component could be used in optical communication and double cladding fiber laser to improve coupling efficiency of pumping light.