Abstract: A residual analysis method for mefentrifluconazole in banana and mango was established using ultra high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) detection technology. The field trial was conducted in banana and mango at six sites during one year according to NY/T 788-2018 the "Guideline for the Testing of Pesticide Residues in Crops" to study the degradation dynamics and residual distribution of mefentrifluconazole. After the application of the formulation of mefentrifluconazole 400 g/L suspension concentration (SC) on banana and mango crops, fruit samples were extracted with acetonitrile, purified with combined adsorbents of GCB and C₁₈, and analyzed by UPLC-MS/MS. The results showed that at four spiked levels of 0.001-1 mg/kg, the average recovery of mefentrifluconazole in whole banana and flesh was 83%-93% with the relative standard deviation (RSD) 2.3% to 5.9%, and the average recovery of mefentrifluconazole in whole mango and flesh was 82%-91% with the RSD 2.9% to 6.0%, respectively; and the limit of quantification (LOQ) was 0.001 mg/kg. The field trials in banana showed that, under the condition of applying mefentrifluconazole 400 g/L SC at dosage of 133.3 mg/kg for 3 times with application interval of 7-10 days, the residues of mefentrifluconazole at 21 and 28 days after the last application were 0.03-0.09 mg/kg in whole banana and <0.001-0.004 mg/kg in the flesh. In the field trials of mango, under the condition of applying mefentrifluconazole 400 g/L SC at dosage of 160 mg/kg for 3 times with application interval of 7-10 days, residues of mefentrifluconazole were 0.04-0.28 mg/kg in whole mango and 0.001-0.003 mg/kg in the flesh at 14 and 21 days after the last application. The research results can provide a reference for guiding the scientific and rational use of mefentrifluconazole in banana and mango, as well as for the establishment of its maximum residue limit (MRL) values.