Abstract: Whispering gallery modes(WGM) optical resonators is an important tool for optical research with broad application prospects. A CaF2 disk resonator was fabricated with ultra-pure single crystal of calcium fluoride characterized by the diameter of 5 mm and thickness of 1 mm. The CaF2 disk resonator was polished with chemical mechanical polishing method and nanometer-scale roughness was achieved. The coupling test platform of disk resonator and tapered fiber was set up to test the optical properties of the resonator. The test results showed that CaF2 optical resonator characterized by the quality factor Q=2.1106 at =1 550 nm. The loss mechanisms of the resonator was analyzed and the method to improve quality factor of the CaF2 resonator was proposed.