In this study, soy isolate protein (SPI)-dialdehyde carboxymethyl cellulose (DCMC) cross-linked gels were prepared by heat treatment at different stages of the gel preparation process. The -NH in SPI reacts with the -CHO in DCMC in a Schiff base reaction to form an imine bond (CN) to achieve crosslinking. The aim of study was to investigate the impact of heat treatment at different stages of the gel preparation process on the mechanical properties, degree of Schiff base reaction, microstructure and rheological properties of cross-linked gels. The results demonstrated that both heat treatment and DCMC could enhance the gelation of SPI. The textural properties of gels were significantly enhanced by heating treatment, resulting in a denser microstructure. Furthermore, heat treatment promotes the degree of Schiff base reaction in gels. In general, it can change the properties of gels by simply altering the heating phase of the gel preparation process.