An improved method to control the incident light power distribution ratio in each core of a multi-core optical fiber is proposed. This method is realized by tapering the multi-core fiber to be a bi-tapered shape after fusing the multi-core fiber with a normal single mode fiber on the condition of core alignment. Based on a coupling theoretical model and analysis, the controlling method is introduced, and the results are demonstrated by both theory and experiment. This incident power distribution controlling method may provide a helpful and potential application prospect for multi-core optical fibers devices and sensors.