The digging spade as one of the essential components of 4U-IA single row potato harvester is mainly used for lifting and transporting the ground substance, including soil, potato tubers, potato roots and grass as well, to the separating device during harvesting operation. With the development of the CAD and FEA, a method was presented for the potato digging spade consisting of a two-plane blade an, a finger-extended spade using a three-dimensional feature modeling software, Autodesk Inventor, based on the virtual assembly associative design, and the FEA progress of the two-plane blade was done by, ANSYS collaborative FEA technology based on the same blade model of CAD The technical essentials of the virtual assembly associative design process were discussed, and as one of the core parts of the whole virtual prototype, the three-dimensional finite element analysis of the two-plane blade modes were performed, the results demonstrated that von-stress and the maximal principal stress were less than the yield limit of material; the safety factor were also satisfied the design requirements.