In this study， superfine grinding technology was used to pretreat defatted egg yolk powder， and the effects of different grinding degrees on the physicochemical and antioxidant properties of egg yolk hydrolysate were explored. The results showed that after the superfine grinding treatment， the particle size of defatted egg yolk powder decreased to 10.87 μm， a high soluble nitrogen recovery rate of 66.23% could be obtained even when the amount of added enzyme was reduced， and it had the best ABTS and DPPH free radical scavenging ability. The correlation analysis showed that peptides with molecular weight of 1-10 ku were positively correlated with antioxidant capacity. In addition， the hydrolysis rate of the defatted egg yolk powder treated by superfine grinding was slower than that of the original defatted egg yolk powder. This phenomenon was related to the transformation of the secondary structure of egg yolk protein from α-helix to β-sheet during the superfine grinding process. On the whole， superfine grinding could effectively improve the yield and antioxidant capacity of egg yolk hydrolysate， which was beneficial to the production of egg yolk hydrolysate.