The optical micro cavity has broad applications because of its high Q characteristic.In this paper, based on the coupling principle of optical microsphere cavity with the tapered fiber,the resonance characteristics of optical microsphere cavity are studied experimentally.The relationship between the voltages and frequencies of phase modulation and the depth change of optical micro sphere cavity has been obtained.The experimental results show that the changes of phase modulation parameters have certain effect on the resonance characteristics(that is,resonant depth) of optical micro sphere cavity. Thus the proper phase modulation parameters should be selected according to the application requirements.