Based on the actual requirements of laser deicing process on the spot size and the action distance, the length and transverse dimensions of the laser deicing optical system are calculated according to the process parameters of laser power and anti-laser damage threshold. Then, the adjustable focusing optical system of high power damage with 100~500 m action distance and 200~600 mm spot size is designed. Focusing on the relationship between action distance, spot size and adjustment focusing distance, the theoretical calculation and simulation are carried out. The simulation results show that this system can achieve the desired adjustable distance and spot, which is verified by actual prototype experiments.