The oil–in–water nanoemulsion of linseed oil and EGCG (LOE-NE) was successfully constructed by ultrasonic treatment. Optimized formula successfully prepared LOE–NE with excellent physicochemical characterization, average particle diameter 160–180 nm, PDI <0.2, Zeta potential ≈−60. Results showed that oil–water ratio had significant effect on the stability of LOE-NE but EGCG did not. Comprehensive characterization and nutritional contribution showed that the emulsion with 1:9 oil–water ratio and 1% EGCG was the best formula. The preferred LOE-NE at low temperature were conducive to reducing the EGCG loss and inhibiting its browning during long-term storage. Further application of the LOE-NE to high–oil foods indicated that addition of 10% LOE-NE and 0.1% neohesperidin dihydrochalcone (NHDC) to salad sauce could improve the sensory flavor, significantly enhancing the antibacterial and antioxidant activities and prolonging its quality stability. Moreover, the addition of LOE-NE can slow down the accumulation of acrylamide and reduce the loss of representative unsaturated fatty acids in the high–temperature baking of mooncakes. These findings will provide new methods and ideas for expanding the food application of high-nutrition linseed oil, and can offer theoretical support and application guidance for the practical development and utilization of nanoemulsion.