This paper introduces three protection functions for brake system of commercial aircrafts. They are the touchdown protection, locked wheel protection and hydroplaning protection . Though the three functions are parts of antiskid protection, they significantly affect the safety and operability of the aircraft. This paper analyzes the purposes of its establishment, the working phases, the principle and control logic for the three functions ,and gives the proposed value of the control logic. Furthermore, the Functional Hazard Assessment (FHA) requirements are analyzed because of the important safety effect. Meanwhile two control schemes are compared and analyzed for the complexity of locked wheel protection , and the conclusion was given.