Abstract: A decoupled identification modeling method in frequency domain is presented to identify the coupled model for a small-scale unmanned rotorcraft.The frequency characteristic in the specified frequency range of the identified coupled dynamic model is obtained by calculating the experimental data,and the coupled dynamic model is obtained by fitting the frequency characteristic.The frequency characteristic calculation method is proposed for the MIMO(multiple-input multiple-output) system,and a multiple coherence function is defined and it is proved that it can be used to express the correlation between inputs and outputs in coupled-channel identification.The longitudinal and lateral angular dynamics coupled model of a small-scale hovering unmanned rotorcraft is identified based on this method,and its influence on rotorcraft simulation model's precision is investigated by adding the coupled model to the rotorcraft simulation model.The comparison between the model prediction output and the actual output shows that the simulation model considering the coupled dynamics can predict the outputs with higher precision than the general model.