The invention provides an air flow distribution device arranged at a cone-shaped reducing part between the outlet of a desulfurizing tower and the inlet of a wet type electric dust collector. The device comprises a flow guide plate and a grid plate. The part from the outlet of the desulfurizing tower to the inlet of the wet type electric dust collector is reduced in a cone shape. The flow guide plate is mounted at the reducing inlet to adjust the trend of the air flow, so that the flow uniform distributing effect is achieved. The grid plate further distributes the flow uniformly at the inlet of the wet type electric dust collector. The device also can serve as an overhaul platform. If the air flow is not uniform, the aperture ratio of the grid plate can be also changed. A purpose of equalizing the flow is achieved by adjusting the resistance, so that the air flow at the inlet of the wet electric dust collector is uniformly distributed. The bottom is overhauled conveniently, so that thewet type electric dust collector operates stably and efficiently, and the demand on ultra-low emission is met.