The preparation and use of gelatins from fish by-products have attracted much attention in the field of food science. Herein, four types of tilapia head gelatins were extracted and characterized: hot water-pretreated gelatin (HWG), acetic acid-pretreated gelatin (AAG), sodium hydroxide-pretreated gelatin (SHG), and pepsin enzyme-pretreated gelatin (PEG). The gel strength values followed the order: PEG (74?±?1 Bloom)?>?AAG (66?±?1)?>?HWG (59?±?1)?>?SHG (34?±?1). The foaming properties, fish oil emulsion viscosity, emulsion activity, and emulsion stabilization ability followed this order: PEG?>?HWG?≥?AAG?>?SHG. The effect mechanisms of extraction methods and gelatin concentrations on the emulsion stability involved the interfacial tension, emulsion viscosity, and fat-binding capacity. This work provided important knowledge for analyzing the relations between the structure and function of gelatin. It also provided a high-value application method of fish wastes.