This study investigates the impact of different milk fat contents on the physicochemical and textural properties of fermented milk, using gas chromatography-ion mobility spectrometry (GC-IMS) and multivariate statistical analysis. The results show that increasing milk fat content significantly improves the water-holding capacity, syneresis, color, hardness, springiness, gumminess, and chewiness of fermented milk, while having minimal effects on pH and total titratable acidity (TTA). Response surface methodology (RSM) optimization revealed that the optimal conditions for producing high-quality fermented milk are 25% milk fat content, 2.5% starter culture inoculation, a fermentation time of 16 hours, and a fermentation temperature of 30°C. GC-IMS identified 36 volatile compounds, with ketone compounds increasing significantly with higher milk fat content. Fourteen compounds were identified as key aroma compounds (ROAV > 1), including benzaldehyde, 2-heptanone-M, 2-heptanone-D, 3-hydroxy-2-butanone-M, 3-hydroxy-2-butanone-D, 2-pentanone-M, 2-pentanone-D, butanal, 2-propanone, propanal, 3-methylbutanal, 2-hexanone, nonanal, and octanal. The electronic nose successfully distinguished samples with different milk fat contents, confirming the impact of milk fat on flavor. These findings provide valuable insights for the development of high-fat fermented milk products.This study investigates the impact of different milk fat contents on the physicochemical and textural properties of fermented milk, using gas chromatography-ion mobility spectrometry (GC-IMS) and multivariate statistical analysis. The results show that increasing milk fat content significantly improves the water-holding capacity, syneresis, color, hardness, springiness, gumminess, and chewiness of fermented milk, while having minimal effects on pH and total titratable acidity (TTA). Response surface methodology (RSM) optimization revealed that the optimal conditions for producing high-quality fermented milk are 25% milk fat content, 2.5% starter culture inoculation, a fermentation time of 16 hours, and a fermentation temperature of 30°C. GC-IMS identified 36 volatile compounds, with ketone compounds increasing significantly with higher milk fat content. Fourteen compounds were identified as key aroma compounds (ROAV > 1), including benzaldehyde, 2-heptanone-M, 2-heptanone-D, 3-hydroxy-2-butanone-M, 3-hydroxy-2-butanone-D, 2-pentanone-M, 2-pentanone-D, butanal, 2-propanone, propanal, 3-methylbutanal, 2-hexanone, nonanal, and octanal. The electronic nose successfully distinguished samples with different milk fat contents, confirming the impact of milk fat on flavor. These findings provide valuable insights for the development of high-fat fermented milk products.