The invention provides a COD (Chemical Oxygen Demand) detection method based on heat changes and a microfluidic chip technology, relates to the COD detection method and in particular relates to a method for realizing COD detection by carrying out heat detection on a microfluidic chip, aiming at solving the problems of a current COD detection method that a period is relatively long and secondary pollution is easy to cause. The COD detection method comprises the following steps: firstly, carrying out heat change detection based on the microfluidic chips; loading a reaction reagent and a water sample in the microfluidic chips respectively and carrying out exothermic reaction; collecting a temperature data peak value and taking the collected temperature data peak value as reaction temperature; obtaining reaction voltage data and a reaction voltage data difference value according to the reaction temperature; realizing the COD detection of a detected water sample according to a linear relation of the reaction voltage data difference value and COD of the detected water sample. The COD detection method provided by the invention is applicable to the COD detection of the water sample to be detected.