The Whispering Gallery Mode(WGM)optical microcavity has a wide range of applications for its high quality factor (Q). Various factors affecting the Q of optical microsphere cavities were analyzed theoretically and experimentally. WGM of microsphere with a diameter of 260 μm was achieved through coupling a tapered fiber. Experiments demonstrated that the water and dust around the microsphere cavity have great effects on the Q, which are mainly the optical absorption loss of water and scattering loss of dust, leading to 1~2 orders of magnitude lower of Q.