The oil drain valve removes air and heat in time in hydraulic fully variable air distribution system. Its performance affects distribution performance of hydraulic fully variable air distribution system. The mathematical and physical modeling of the drain performance of the new drain valve, namely, the drain time and the drain quality, was carried out. Using dynamic mesh 6DOF technique combined with single factor test, the influence of inlet pressure, valve opening, valve ball mass, preload force and spring stiffness on oil drain performance was studied. The single factor test reveals the influence law of each parameter on oil drain quality and oil drain time, and verifies the correctness of the mathematical physical model.