A new aided diagnosis of oral cancer was developed for the separation and analysis of nitrosonaphthol reactant（NNR) of urine in oral cavity cancer patients by using high performance liquid chromatography with fluorescence detection（HPLC／FLD),based on the analysis of urine NNR of 34 cases of oral cancer patients and 18 healthy people and their difference of composition content.The experimental results showed that a marker with excitation wavelength of 440 nm and emission wavelength of 539 nm,could be detected in urinary nitrosonaphthol reactant（NNR) from healthy people and patients with oral cavity cancer under the condition of this paper.The marker content was relatively low in oral cancer patients and significantly high in healthy persons,which is quite different from the usual test results.Significant differences were found in the matter content in healthy people and those with oral cancer patients（P<0.01) using a non parametric test （Mann-Whitney U test).Further data analysis showed that the specificity was 94.1%,the sensitivity was 94.4%,the area under the ROC curve（AUC) was 0.989.The model showed a high diagnostic value,and could be used for the auxilary identification of oral cancer.