The conventional radar theory relies on the classical electromagnetic wave theory to run. On the contrary, a quantum radar will relie on the quantum mechanic theory to run. A quantum radar that uses the quantum illumination based on photon entanglement enables to get a better detection sensitivity. In this paper, we highlight the influence of the propagation environment on the quantum illumination radar scheme. Our approach consists in describing the quantum information evolution inside the radar and the entanglement rate with a mathematical parameter which represents the interaction strength of the propagation medium on the quantum system used by the radar.