Abstract: In this paper, a two-parameter model is proposed to identify the viscosity coefficients of composites. These two parameters are the viscosity coefficient of resin and the viscosity coefficient of carbon fiber in the woof direction respectively. The parameters were identified by using the field measured damping ratio of a cantilever gird, and tested by using the field measured results of other girds. In identifying, the influence of air resistance is taken into account. The result of analysis shows this method is effective, and its error is agreeable.