Surface topography (as Roughness) and gloss of the thermoplastic are affected by varying in painting parameters greatly. Gloss of thermoplastic reflects light through the surface in a specular direction, it is a quality factor in the visual test of final products. Surface roughness of a thermoplastic had a role in determination of optical behaviour and aesthetic appearance. The experiments presented in this paper shows the effect of painting parameters changing on gloss and surface topography of thermoplastic parts. Eight painting parameters were chosen to study their effect. Gloss and roughness measured for the molded samples which molded in a mold-cavity with a rectangular impression in Arburg all-rounder 320C- 600250/molding machine (figure 1) that mounted at conveyor of an automated spray-painting machine. And then the parameters of painting (material pressure, gun height, oven drying temperature time, and gun angle) were changed each trial to see its effect