Photochemical machining (PCM) is a process of metal corrosion in which by using light and Photoresist, desired areas are selected and machined in etchant.Among advantages of photochemical machining are the lack of mechanical and thermal residual stresses in the work-piece, being burr-free after machining, the lack of change of hardness and toughness of materials and higher dimensional precision.Considering the above mentioned advantages of this method, the wide range of various industrials such as horology, military, medical and optical industries is. Regarding the need of gears in small scales (diameter and thickness),it is important to use modern methods of machining which produce minimum mechanical and thermal residual stress in the workpiece. Photochemical machining is one of these processes that is under study in the present research. Some effective parameters of PCM have been investigated in order to produce gears with thickness of 0.5mm, external diameter of 9 mm and number of teeth 16. By using a template, there would be some limitations such as the need for preparing the films with high accuracy and aligning it with workpiece resulting in more complexity and cost.In this study, the initial experiments have been done on the slide (lam) in order to preliminarily investigate the light exposure device and applied lenses (microscope and lens) as well as to find the effect of exposure time interval and centrifuge speed on the quality of gear teeth. After preliminary tests, the fact was concluded that it is better to use simple lens with less effective openings for reducing the energy intensity of light shone to photoresist. Various types of acids such as HCl , HNo 3 , H 2 O 2 , FeCl 3 and Acid citric were studied inorder to suggest a suitable etchant for brass material removal. these tests led to apply an etchant with the composition of come H 2 O, HCl, FeCl 3 and H 2 O 2 . Mixture design was used to achieve the appropriate etchant based on DOE methods and the tooth thickness on the step circle was measured as the response. Tests were carried out while other parameters such as exposure time and a Centrifuge speed were fixed. In conclusion, Obtained appropriate etchant was combination of 53g H 2 O, 39g HCl ,4.7g FeCl 3 , 2g H 2 O 2 .Moreover, Response surface design was applied to study the influence of exposure time, rotation speed of spinner and duration of spinner rotation. Data analysis showed that the square of exposure time and rotation speed would have a significant effect on tooth thickness on the step circle. Subsequently, the gears with 0.06 tolerance in tooth thickness on the step circle was produced through the tests. Key words:Photochemical Machining, Spur gear, Mixture design, Response Surface