Abstract: In order to realize mechanized direct seeding of rice，a air-suction precision metering device for rice was designed.Working principle of metering device was expounded.Structural parameters of metering device were determined by the theoretical calculation，which contained the suction hole diameter and negative pressure.In order to verify the performance of seed-metering device and find the best parameter combination，orthogonal test was carried out by using the eligible index，multiple index and missing index as experimental indexes.The optimal experimental results were：suction hole diameter of 1.4 mm，rotating speed of seed tray of 40 r/min and negative pressure of 1.8 kPa，and corresponding performance indexes were as following：eligible index was 82.91，multiple index was 11.56 and missing index was 5.53，which could completely meet requirement of technical specifications of quality evaluation.