The invention relates to the field of wastewater treatment, in particular to a method and process system for treating wastewater. The method uses zirconium hydroxide to adsorb pollutants in wastewater, can simultaneously remove phosphate, organic matters and sulfate in wastewater, and further can reduce the phosphate in wastewater or effluent to 0.2mg/L and COD to 20mg/d in a short time while treating wastewater containing the low-concentration phosphate and the organic matters or the effluent subjected to the conventional wastewater treatment, so that phosphorus and COD in final effluent meetthe water quality of class III water in the Surface Water Environmental Quality Standards (GB3838-2002); when wastewater with high-concentration pollutants is treated, the adsorption amount is largeand the adsorption efficiency is high, for example, when the phosphate concentration in wastewater is as high as 5000mg/L and the COD concentration is as high as 6000mg/L, the adsorption rates of thephosphate and COD are up to 96.2% and 92.1% respectively within 30 min.