Abstract: Provided is a wastewater treatment method including measuring a chemical oxygen demand (COD) of wastewater containing organic matter in real time, calculating the amount of ozone associated with a concentration of the organic matter using the measured COD value, and controlling a production of ozone of an ozone generator based on the calculated amount of ozone. The present invention provides a wastewater treatment method and system for adjusting the production of ozone used as an oxidizing agent for decomposing organic matter in wastewater in association with a load of organic matter in wastewater to be oxidized.