Ring resonators have been playing a very important role in the design and fabrication of active and passive optical devices due to their small size, multi-function and compactness. Bend loss characteristics of optical fiber are investigated thoroughly, and the results show that all-fiber resonator with smaller ring radius, wider free spectral range (FSR), higher fineness (f) and quality factor (Q) can be achieved only by microfiber. Based on the improved fused taper technique, under the condition of slow change and adiabatic condition, a 5 μm-radius high-quality microfiber with uniform waist length of 80 mm is fabricated. And utilizing self-wrapping coupling method, an all-fiber microring resonator with 500 μm radius is realized, which exhibits good resonant response. This all-fiber device is expected to avoid the large bendloss and connection loss induced by planar waveguide integration.