The utility model provides a low-temperature ball valve specially for a low-temperature working condition less than -40 DEG C. The low-temperature ball valve comprises a valve rod, a lengthened body, a valve body, a valve cover, a ball body, a sealed valve base, a spring, a stuffing box gland, an auxiliary valve base, and a valve base spring. The auxiliary valve base which is in tight contact with the ball body is arranged on the medium entrance side of the ball body; a valve body cushion is arranged at the bottom of the auxiliary valve base; and the valve base cushion is tightly pressed to the auxiliary valve base through the valve base spring mounted on a valve cover drill hole. With the adoption of the low-temperature ball valve provided by the utility model, the pressure leakage problem of a middle cavity and the turn-off problem when a medium pressure is low can be solved.