Abstract: In order to make laser etching on the semicircle accurately, engrave the hemispherical platinum resistance of heat flux sensor and meet the precise positioning of the heat flow measurement points, the method of positioning processing point based on the vision imaging system was used. After theoretical analysis and experimental verification, the positioning data of high platinum resistance was gotten. Firstly, the edge contour was illuminated by the backlight and was visible clearly. Then, after extracting four coordinates on the edges, the hemisphere vertex was calculated. After rotating the platform and compensating the deviation value, the precise processing position was found. Finally, the resistance position of the heat hemispherical sensor was measured and verified. The experimental results show that the method has good positioning effect, the relative error of sphere radius by corrosion is about 0.39%, the relative error of rotation angle of loading platform is controlled in 3.9%. The problem of positioning hemisphere vertex is solved and the precision of laser corrosion is raised. This study is helpful to make platinum resistance on curve surface model by laser.