SLA (Stereolithography Apparatus) it a process used to rapidly produce polymer components directly from a computer representation of the part. Though SLA is being recognized as an innovative technology, it still cannot be used to fully practical application since it lacks of dimensional accuracy compared to conventional process. If the shrinkage were perfectly uniform and no distortion took place, excellent part accuracy could still be achieved through and appropriate scaling factor when generating the build file. However, in certain geometries involving intersecting thick and thin sections, nonuniform retrain shrinkage becomes the engine of part distortion. In order to improve the part accuracy of SLA, this paper evaluates how largely each parameter of SLA contributes to the part accuracy and estimates the optimal set of parameter which minimizes the dimension error of the test part, "Slab (100mm$ imes$100mm$ imes$2mm)"and "scale bar"part. Three control parameters such as critical exposure, generation depth and fill cure depth are used.