The invention discloses a painting robot position planning method for a large-scale free-form surface and relates to the technical field of robot painting. According to the method, firstly, a spray gun track planning method is adopted to complete blocking of the large-scale free-form surface and planning of a spray gun track; then on a specified position search cone generatrix, a point in a working space of a painting robot and a three-dimensional moving platform is selected and a joint angle and a joint angular velocity in the painting motion are solved out by utilizing the robotics principle so as to carry out feasibility checking on the point; next, collision interference check is carried out by utilizing a motion simulation function of three-dimensional shaping software; finally, all feasible positions corresponding to free-form surface blocks are found. The painting robot position planning method for the large-scale free-form surface can implement batch position planning on a plurality of free-form surface blocks in the large-scale free-form surface and has a high calculating speed and a high automation degree.