Abstract: The effects of coffee concentration(12.5%,25% and 50%)on the stability and digestive behavior of coffee milk systems were studied. Turbiscan Lab multiple light scattering instrument,Malvern nanoparticle size/potentiometer,confocal microscope and other instruments were used to evaluate the stability of the coffee milk. The behavior of the milk in vitro simulate gastric/intestinal digestion were studied. The results showed that with the increase of coffee concentration,the system stability index(TSI)increased from 1.2 to 2.1 within 1 h,the average particle size increased from 306 nm to 643.6 nm with single peak changing to double peak in the particle size distribution pattern,and the potential value reduced by 6. There was no significant difference in protein electrophoresis band between different coffee concentration systems in vitro simulate gastric and intestinal digestion. However,the obvious droplet aggregation occurred in 25% and 50% concentration coffee system at the 1h stomach digestion stage. The increase of coffee concentrations led to a decrease in the stability of the system and aggregation of oil droplets in vivo stomach digestion,however,there was no negative effect of it on the digestion of the protein in the system.