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Sudan dyes are banned as food additives due to the carcinogenicity of their metabolites in the human body. Therefore, it is of great significance for sensitive detection of Sudan dyes. This paper reports a novel nanosensor for Sudan dyes detection based on fluorescence (FL) quenching of hexadecyl trimethyl ammonium bromide (CTAB) stabilized upconversion nanoparticles (UCNPs) through the inner filter effect (IFE). In the presence of Sudan I–IV, the fluorescence emission of UCNPs was effectively quenched due to the absorption bands of Sudan I–IV largely covered the emission bands of UCNPs. Under the optimized conditions, the FL was quenched with Sudan concentration over the range of 0.05–40, 0.01–20, 0.01–40 and 0.05–40 μg/mL for Sudan I–IV, respectively. The corresponding limit of detection is 15.1, 2.83, 3.52 and 16.7 ng/mL (at 3 σ /slope) respectively. Meanwhile, the nanosensor shows good selectivity, sensitivity and can be successfully applied to detection of Sudan in chili powder samples. [ABSTRACT FROM AUTHOR]