Power kite energy systems use power kites attached to the ground by tethers that transfer the wind mechanical power to ground electrical generators. In order to remain in the air, the power kite should fly continuously in “lying” eight form trajectories. One key to the optimal operation of this system is automatic control of the kite flight, requiring a reliable real-time position measurement and advanced closed-loop control of the position and speed of the kite during its flight. The basis of a good controller is the identification and modelling of the dynamic system. This is the purpose of the current work. A power kite system prototype is built and identified on the basis of input-output data. Validation of the obtained model is also provided.