Laser-fused fiber taper optical coupler features a significantly smaller package in comparison with conventional flame fused coupler and was ready to fit in modern compact devices. An algorithm was proposed for the design of the microcoupler and a 3 dB microcoupler with a fused length 200 μm was presented. As an effort to search for optimal low loss coupling,optical properties of the micro-coupler were studied for various taper lengths from 1000 to 6000 μm as well as for different diameters in coupling region. Beam Propagation Method (BPM) was used to simulate the operation of microcoupler and the theoretical result was compared with measured property. An optimum design was found at a taper length of about 1320 μm and coupling diameter of 14 μm with an excellent coupling efficiency.