In this research the production of citric acid by solid state cultivation has been investigated. Apple residue as substrate and Asperiginase Nicher PTCC 5010 were selected. The effects of temperature, moisture, substrate particle size, nitrogen and carbon sources based on reminded glucose have been studied. In this experiment, the acid production increased from 27 gram (per one kilogram apple residue) to 127 gram. The results clearly proved optimization and development of citric acid production in comparison with pervious processes.