The invention discloses a water treatment system based on an ozone and biological activated carbon combination technology. The water treatment system comprises an ozone preparation unit and a water treatment unit, wherein the ozone preparation unit comprises at least one ozone unit, an air source unit and a cooling unit; the air source unit and the cooling unit are respectively connected with an oxygen inlet and a cooling liquid inlet of each oxygen unit; the water treatment unit comprises a pre-oxidation tank, a post-oxidation tank and a biological activated carbon filter which are arranged successively; and the pre-oxidation tank and the post-oxidation tank are respectively connected with an ozone outlet of each ozone unit. The invention further discloses a treatment method of the water treatment system. The treatment method comprises the following steps: (1) carrying out pre-oxidation treatment on raw water to be treated and ozone prepared by the ozone preparation unit; (2) carrying out deep oxidation treatment on water obtained from the step (1) and the ozone prepared by the ozone preparation unit; and (3) carrying out biological activated carbon filtering treatment on the water obtained from the step (2). The treatment system and method are high in automation degree, high in treatment efficiency and low in energy consumption.