The decrease of colloidal suspended particles density, which is the main factor of water treatment, continually, it is one of the aims of refineries design of superficial water treatment plans.The most common way in omitting of these particles is coagulation/flocculation/sedimentation/filtration. Mineral coagulants are frequently used for coagulation. Because of harmful metals including Aluminum and impurities as polluted monomers and heavy metals in this kind of coagulants, the use of natural organic matter as Chitosan and moringa oliefera has been recently taken into consideration. This research was mainly to examine the performance of Chitosan in omitting of natural waters turbidity. So the effect of Chitosan and Poly-aluminum-chloride on the sample of Zayandehroud river were examined via Jar test. The result shows that Chitosan can omit suspended particles in water in very low dose (about 0.5 mg/L). Setting the optimum program of jar test showed that among parameters of Jar test, speed of rapid mixing has more effect on output of turbidity omission by Chitosan. The Jar test on waters which have different primary turbidity showed that Chitosan performance in turbidity omission, depends on suspended particles density in water, in such a way that omission output in low turbidity was significant and would increase with the increase of turbidity. In order to examine the Chitosan performance in pHs, the turbidities an doses of different use, at first factorial design of experiments was defined. The analysis of finding obtained from experiments done by the analysis of variance showed that the turbidity omission output is independent of the dose of coagulant use and depends on the raw water pH and primary turbidity of water. Also, Chitosan can decrease the water turbidity witch includes pH and different turbidities down to 25NTU. Even in low doses (0.5 mg/L). the jar test in different temperature showed that the turbidity omission output will be done by Chitosan which is independent of the raw water temperature. Also, the experiments showed that sedimentation and flocculation processes in coagulation by the Chitosan will be completed in a shorter time than that of the frequent coagulants.