Main aim of this study was evaluation of Poly Aluminum Chloride and Ferric Chloride’s impacts, as two ordinary coagulants in water and wastewater treatment industry, on Phosphorus removal from wastewater treatment effluents. This research was established on Isfahan north wastewater treatment effluent. Taghuchi method was used as examination design method’s for finding the optimum terms that cause be gain maximum removal of Phosphorus. Samples were collected monthly for six months. Results of analysis suggested optimum level for coagulant dose, pH, time and tensity of rapid mix, time and tesity of slow mix and settle time. Samples, after collection was carried to environmental laboratory in civil engineering factually on Isfahan University of technology. pH, Turbidity, COD, total phosphorus and alkalinity was determined, early. In each experiment series did 18 tests according to orthogonal array witch suggested by Taghuchi method. Then suggested levels were evaluated. In total cases Taghuchi method prediction’s accuracy were more than 93 percent in removal of phosphorus. When all of tests in six months completed, Analysis of Variance (ANOVA) was established to identify of share ratio for each parameter in phosphorus removal process. For each series of experiment a General Linear Model (GLM) was created with Minitab software. Interactions effect between main parameters was assessed for generation of a good model, too. Totally impact of any parameter on removal of phosphorus specified with contraction of 6 models for each coagulant. In cases of using Poly Aluminum Chloride, coagulant dose, settle time, pH, slow mix tensity, slow mix time, rapid mix tensity, rapid mix time had ordinary share of 30.92, 19.06, 17.60, 9.48, 8.16, 8.06 and 5.29 percent. In cases of using Ferric Chloride the shares were different. pH, coagulant dose, rapid mix time, settle time, rapid mix tensity, slow mix tensity and slow mix time had share of 29.81, 15.57, 13.95, 13.69, 11.07, 9.69 and 4.13 percent, ordinary. Maximum efficiency of phosphorus removal with poly Aluminum Chloride was 89.9 percent with residual phosphorus 0.1 mg/l. Also maximum efficiency of phosphorus removal with Ferric Chloride was 98.8 percent with residual phosphorus 0.4 mg/l. Impact of dosing Ferric Chloride on pH decrease was great. Key Words : hosphorus, Coagulation Flocculation, Poly Aluminum Chloride, Ferric Chloride, Taghuchi