By reasonably predigesting the characteristics of the subminiature rotorcraft, a model for the nonlinear dynamics of a subminiature rotorcraft is established. Through the linearization of the nonlinear dynamics, the linear time-invariant attitude dynamics with physical parameter of the subminiature rotorcraft at hover is obtained. A subspace-based state space system identification method is applied to identify the model of rotorcraft; the percent standard deviation for each parameter is also obtained. At last, the valid of the identified attitude model is testified.