The utility model discloses a static balance adjustment ball valve and relates to a valve structure for medium cutting off and flow adjustment for heating, ventilation and air conditioning systems. The ball valve mainly comprises a valve body, a valve seat, a ball valve core, a valve rod, a non-return unit, a flow adjustment mechanism, a flow limit mechanism, a handle and the like. The opening degree between the ball valve core and the valve seat is adjusted and limited by the flow adjustment mechanism on the valve rod and the flow limit mechanism on a location disc together, and accordingly, the valve flow is balanced and regulated. Meanwhile, the non-return unit is added at the outlet end of the valve body, so that the valve is provided with a non-return function; a pressure measuring joint and a temperature measuring joint can also be arranged on the valve body, so that the flow and the temperature of the valve can be measured conveniently; besides, various joints are arranged at the inlet end of the valve body, so that users can use the ball valve flexibly conveniently; the improved static balance adjustment ball valve has the advantages of being simple in structure, small in flow resistance and opening and closing torque, capable of being used flexibly and the like.