Reducting conditions is one of the most important problems in the cement factories that decrease the cement quality and strength. Microscopical analyses are one of the easiest methods that can provide information about qualitycontrol and trouble-shooting situations in kilns quickly. In this research reducting conditions in the Fars cement factory coarse clinkers were investigated by preparing 10 polished sections from rim layer to core, SEM pictures and Ono method. Based on these methods, because of high burning time and creation the reducting conditions in kiln, alite crystals alteration in to belite crystals and limestone that can be seen in clinker’s core polished sections with abundant of belite crystals. More fractures were produced in clinker cores by Reducting conditions and cause the low strength in mortar and concrete. Also heating and cooling rates were slow and maximum temperature was long in the Fars cement factory clinkers generation.