In this paper, we present a new method for soft landing of an unmanned aerial vehicle (UAV) on a ground robot based on impedance control. It is applied for a heterogeneous robotic system aimed at warehouse stocktaking automation. We describe the operating and mathematical principles of the impedance control for the landing system of the UAV and present the results of the real-world experiments. We evaluate the softness of landing using force sensors attached to each of four legs of the drone by measuring the impact force during the contact. Experimental results revealed that proposed landing impedance control decreased the impact force by 60%. The proposed approach can also be applied for delivery drone landing on the moving truck, cargo ship, or uneven terrain providing low risk of crash accident.