In order to solve the problem of the single metering device in the series of 2BFQ precision planter is single row seeding, low efficiency and high space usage, a precision pneumatic metering device for rapeseed was designed. To determine the inlet and outlet hole’s structural parameters of pneumatic rapeseed precision metering device, the distribution of internal flow field in the metering device has been studied analytically and numerically. The influence of diameter of hole, number of hole and diameter of flow outlet on the performance has been studied by using the 3D modeling software of CFX and Pro/E . The simulation results were verified by experiments. The results showed that the three factors are all important to influence the negative pressure and inlet flow velocity distribution of holes’ end face. When the diameter of hole is 1.2 mm, the number of hole is 40, the diameter of flow outlet is 25 mm and the rotating speed is 15 r/min, a negative pressure is achieved to be 1 400 Pa with positive pressure of 400 Pa. And then, the quality index of single seeding can reach 89.99%, low sowing index is below 5%, the consistency variable coefficient of double-row qualified index and miss index is below 3%, which meeting the requirements of rape meter sowing technology.