Automatic robot trajectory generation for thermal spray applications is considered necessary for advanced automatic manufacturing. Achieving coating uniformity on the free-form surfaces is the principal challenge due to the complexity of their geometries. The purpose of this study is to develop a new function of Thermal Spray Toolkit with user-friendly interface for automatic generation of robot trajectory on the irregular workpieces according to the spray parameters, such as the torch speed, the spray distance, the spray angle, etc. This software toolkit is based on RobotStudio which is an off-line programming and simulation software by ABB company. The results showed that the robot trajectories can be generated rapidly, accurately and automatically on the free-form surfaces by using Thermal Spray Toolkit.