In normal conditions, pressure drop, in the labyrinth minimum flow valve, mainly concentrates on the first several levels of the labyrinth channel in throttle disc, which may cause easily the strong erosion of the valve material. To improve the flow characteristics of the throttle disc in the labyrinth minimum flow valve, the connecting groove is added the disc to connect all the labyrinth channels. With CFD numerical simulation, flow characteristics, such as flow field distribution, pressure drop curves and flow velocity curves in each level, of the minimum flow valve with and without the connecting channels are compared. Results indicates that pressure drop distribute more uniformly on all levels after the connecting groove is added. And local areas of abrupt pressure change are reduced, in which case cavitation is not easy to occur. In addition, the mean flow velocity in each level also decreases by using the connecting groove, which is beneficial to reduce the vibration and noise of the minimum flow valve. Corresponding to the larger flowing space in the throttle disc with connecting groove, the outlet flow velocity increases slightly. Besides, the connecting groove as well improves the inlet flow state of the disc sleeve, changing the swirl transition to smooth transition. And it makes the valve work more stable. In general, connecting groove improves the flow characteristics of the minimum flow valve and it of great referential significance for improvement of other valves.