In order to accurately describe the contribution of extracellular polysaccharide (EPS) to the rheological properties of the gel in the complex system induced by lactic acid bacteria fermentation, acid-induced soy protein isolate (SPI) was used as the model. The effect of exopolysaccharide produced by Lactobacillus casei (CEPS) on the macro rheological properties and microstructural changes of acid-induced SPI gel were analyzed by scaling model and image analyses. The estimated value of storage modulus (G') at time infinity, gel point, G' at 37 °C, enhancement effect of G' during cooling (ΔG'), recovery rate, critical strain (γc) and fractal dimension (Df) exhibited strong CEPS concentration dependence. The addition of CEPS led to the formation of uniform and compact three-dimensional network, which was mainly represented by small voids and apertures. Therefore, by reducing the complexity of the fermentation gel system, this study explored the effect of CEPS on the rheological properties of fermented soy protein gels and the fermented soybean protein gel with good rheological properties can be selected by quantitative image analysis.