Abstract: Pesticide residues in food seriously damage consumers' health, and research on novel detection methods is of great significance for ensuring food safety. Upconversion nanoparticles (UCNPs), characterized by high fluorescence intensity, strong anti-interference ability, and ease of modification, have become a research hotspot in the field of food safety detection. This paper systematically reviews the synthesis and modification of UCNPs and their related research in pesticide residue detection, with a focus on the advantages and disadvantages of synthesis methods such as thermal decomposition and co-precipitation, hydrophilicity and targeting surface modification strategies, and the detection performance and sensing mechanisms for pesticide residues including organophosphorus, neonicotinoid, pyrethroid, carbamate, and benzimidazole classes. Future research should focus on signal amplification, real-time detection, and standardization to expand the application scope of UCNPs-based detection methods.