The mechanical transfer characteristics of single mode quartz fiber optic sensor with double coating is studied. The theoretical model of linear elasticity between quartz fiber optic with double polymer cladding coating and buffer are presented. The theoretical results demonstrates that the mechanical transfer characteristics of double coating depend on the relative magnitude of elastic modulus between cladding and buffer under the small radius approximation compared with the model of single coating. When the elastic modulus of buffer is much bigger than that of cladding,its action can be neglected. In the experiment,the experimental study on the average transfer coefficient of different scale fiber optic sensors embedded in the matrix material has been carried out based on white light interference method and the result of experiment accords well with that of theory.