The invention relates to a full coverage motion path planning method for agricultural machinery, and relates to the technical field of path planning of unmanned agricultural machinery. The method comprises the following steps: firstly, using a Boustrophedon decomposition algorithm to divide a target farmland and obstacles into a plurality of adjacent areas, and assigning each area with a K value,wherein the K value indicates whether the area is covered or not, the K value is equal to 0 when the area is not covered, and the K value is equal to 1 when the area is covered; then, using a geneticalgorithm to find an optimal path covering all the areas; when an agricultural machine performs a straight-line round-trip operation within the area, enabling the agricultural machine to retrieve theK value while operating according to the planned route, and if the K value is 0, operating according to the route; if the K value is 1, moving to the next area; in order to avoid repetitive operationin the covered areas, introducing an A* algorithm to find the optimal path along which the agricultural machine can reach the next area, and so on until all the areas are fully covered. Compared withother technologies, the technology provided by the invention realizes higher ground coverage rate, and also increases the operation efficiency, reduces overlaps and omissions, and saves time and energy.