A conversion method from cartesian space trajectory to joint trajectory of spray painting robot based on Dijkstra algorithm was presented to meet the requirements of offline programming spray painting robot and characteristics of spray cartesian space trajectory. Through analyzing the relations between the part coordinates and the robot basal coordinates, the spray cartesian space trajectory was converted to the robot basal coordinates by three points calibration of auxiliary feature points. An optimized model was established to obtain the shortest joint motion distance in robot inverse kinematics solutions. The distance between all of the inverse kinematics solutions was described by a directed weighted graph, and the Dijkstra algorithm was employed to obtain the optimal combination of inverse kinematics solution. Finally, the feasibility and efficiency of the method were verified by spray experiment.