This study aimed to prepare Maillard reaction products (MRPs) from whey protein isolate (WPI) and different reducing sugars (glucose, fructose, maltose, lactose), and utilize the optimal MRPs to fabricate tuna oil (TO) microcapsules for enhancing TO's storage stability. The results showed that the optimal wet heat reaction duration of WPI and reducing sugar was 8 h at 75 °C. Glycosylation improves the functional properties of WPI. WPI-maltose coupling (WPI-M) and Arabic gum were selected as the wall material to prepare TO microcapsules by complex coacervation, and the encapsulation efficiency of microcapsules reached 87.41 %. Compared to WPI, WPI-M microcapsules have a more homogeneous emulsion morphology. The peroxide value of microencapsulated protected TO was 35.78 % lower than that of free TO after accelerated oxidation at 55 °C for 16 days. Microcapsules prepared with MRPs wall materials by complex coacervation offer a promising approach for the preservation of compounds.