Abstract: In view of the difficulty of collecting alfalfa seeds in our country, low production yield and quality of grass seeds, long-term dependence on imports, low harvesting mechanization, large-scale, intensive, standardization, and lack of special harvesting equipment, etc., this article discusses the new type of self-propelled forage seed harvesting equipment, introduces the physical characteristics of alfalfa plants, material suspension characteristics, overall structure schemes and working principles, and completes the structural design and parameter calculation of walking chassis, the threshing collection platform before cutting and the settling box and other key components, the simulation analysis of the internal flow field of the threshing collection platform before cutting was completed, and the average velocity at the entrance of the collection platform was obtained. the error was within the allowable range and was greater than the suspension velocity of seeds and seed pods. It also verified the material suspension characteristics test rationality. Field performance tests were conducted on the prototype, and the prototype was optimized through the analysis of test results and technical indicators. The test results show that the various technical performance indicators of the machine can meet the design requirements, and it can complete the threshing and collection of standing alfalfa seeds before cutting, wind negative pressure conveying, depressurization and settlement, and auger conveying and loading, etc.,the quality is good, the harvested seeds, pods, broken stems and other material mixtures are uniform and pure, and the corn grass is relatively small, which provides a good raw material basis for subsequent cleaning operations. At the same time, it also provides new type of special harvesting machine for forage seeds for our country. The self-propelled structure is simple and compact, and it is free to move. The loss rate of the threshing collection before cutting is small, and the results are worthy of transformation and demonstration.