In this study, soy protein isolate (SPI) and xanthan gum (XG) were used as the matrix to combine with corn oil for the preparation of a composite emulsion gel. By comparing six oil addition methods, the effect of the emulsion gel on the sensory properties, texture, rheology, microstructure, and oxidation stability of composite fish sausages was systematically investigated. The results showed that compared with traditional methods such as direct oil addition and the addition of single or combined emulsifiers, the SPI-XG composite emulsion gel formed a denser three-dimensional network structure and consequently exhibited significantly enhanced gel strength (P < 0.05), with the smallest bending angle of 5°. It also exhibited the highest water-holding capacity, with the lowest cooking loss rate (7.03%) and emulsion loss rates (2.63% for total juice loss and 2.33% for oil loss). Moreover, this system effectively inhibited sausage oxidation, resulting in markedly lower peroxide value (7.27 mmol/kg) and carbonyl content (22.71 nmol/mg) compared with the other groups. The SPI-XG composite emulsion gel provides an innovative and effective solution for reducing the quality deterioration of high-fat surimi products and developing high-fat surimi products with good quality and stability.