Abstract: Real time test and control over seed-selecting process gravitational seed selecting machine based on virtual instrument technology can be realized. With the help of Labview, some parameters are adjusted through comparing weight of seed selected with presetted one. The parameters are longitudinal and transverse obliquities, vibrating frequency of work table, wind fluxing on work table. It makes seed selecting parameters of gravitational seed selecting machine achieve optimum adjustment. One-thousand-grain seed weight is guaranteed in reaching the presetting level. The system of test and control over gravitational seed selecting machine based on virtual instrument techology is more convenient and direct in use compared with traditional way.