The invention discloses a workpiece following grabbing locus planning method and system used for a high-speed sorting system. The method comprises steps of establishing a following grabbing locus model, acquiring workpiece coordinates, manipulator end coordinates and manipulator movement parameters; according to the workpiece coordinates, determining conditions of workpiece loci and determining acurrent solving interval; according to the current solving interval, determining the interval displacement and a time formula, and determining the value range of a single variable in the interval; according to upper and lower half regions of the working range where the workpiece is arranged, determining a grabbing equation of locus; substituting the displacement and the time formula into the equation of locus; using the bisection method to solve the solution of the equation of the locus in the value range, if there is a solution, according to the equation solution, planning a grabbing locus and executing the grabbing; and if there is no solution, turning to the next solving interval and repeating the solving processes. The beneficial effects are that the working range of the manipulator are fully used; the characteristics of the S curve speed increasing and decreasing algorithm are fully used; grabbing efficiency is improved; and grabbing precision is improved.