Four ferulic acid alkyl esters were obtained by the direct esterification reaction of ferulic acid with the respective alcohols (ethanol, butanol, octanol and dodecanol). The antioxidant efficiencies of ferulic acid and its alkyl esters in bulk methanol solution and in 28 rapeseed oil-in-water emulsions were determined by the DPPH assay and the Schaal oven test, respectively. Results showed that ferulic acid had the highest antioxidant efficiency in methanol solution, with its DPPH scavenging abilities 0.967 mmol Trolox/mol. Ferulic octyl ester has a maximum of antioxidant efficiency in rapeseed oil emulsions. For the emulsions with the addition of ferulic octyl ester at the volume fraction of emulsifier 1.0% and the oil to water ratio 28, the time to reach a conjugated diene value of 1 and the p-anisidine value of 6 was 51 and 40 d, respectively. The pseudophase kinetic model was used to determine the percentages of ferulic acid and its alkyl esters in the interfacial region of the emulsions. The results showed that ferulic octyl ester was the most efficient antioxidants in the emulsions because its percentage in the interfacial region was highest.