The invention relates to a method for rapidly determining COD of waste water difficult to be oxidized, which adopts a titanium plate as a substrate electrode; vertical and ordered TiO2-NTs are grown on the titanium plate surface; a SnO2/TiO2-NTs sensing electrode with photoelectrocatalytic integrated oxidation performance is obtained by pulse electrodeposition of tin antimony oxides, which can be used for COD determination of waste water difficult to be oxidized. Compared with the prior art, the construction method of the sensing electrode in the invention, on one hand, allows most SnO2 to enter TiO2-NTs but not to completely cover TiO2-NTs, which facilitates direct light irradiation on TiO2-NTs, and brings into full play of its photocatalytic effect; on the other hand, tin antimony oxides are codeposited inside the TiO2-NTs simultaneously, which significantly increases the oxygen evolution potential, obviously improves the electrode oxidation capability, provides more superiority than a layer-by-layer deposition method, and facilitates the performance of electrode catalysis. The SnO2/TiO2-NTs sensing electrode prepared by the invention has photoelectric integrated strong oxidation performance, so rapid COD determination of waste water difficult to be oxidized can be realized.