The invention relates to a water purification method for landscape water. The water purification method for the landscape water is performed by using a magnetic separation system and mainly comprises the following steps of: separating the landscape water through slag removal, coagulation, mixing, flocculation and magnetic separation systems in turn, directly discharging the separated effluent to the landscape water system, reclaiming magnetic particles from big magnetic particle substances through a magnetic reclamation system to recycle, and concentrating the reclaimed residual sludge. The water purification method for the landscape water has short flow and short treatment time, can remove over 75 percent of inorganic phosphorus, over 90 percent of suspension and partial chemical oxygen demand in 3 to 4.5 minutes, and has high treatment efficiency; the generated sludge amount is 0.05 to 0.1 percent, and the water content of the sludge is less than 96 percent, so the difficulty of sludge treatment is effectively reduced; and the method has low running expense, saves the floor of equipment and facilities, is convenient to manage and convenient to start and stop, can run continuously or intermittently, and has strong adaptability.