Abstract: Peanut protein is a kind of plant protein with high nutritional value. However, there is a lack of high-value-added peanut protein products. Extrusion processing has the advantages of easy operation, safety, green environmental protection, and continuous output. The puffed peanut protein products produced through extrusion technology will broaden the application of peanut protein in food, thereby enhancing its added value. Nevertheless, peanut protein has issues with poor expansion effect and quality properties (texture and rehydration properties) during extrusion processing. In order to expand the application of peanut protein in extruded food and solve the problem of poor expansion effect and quality properties, this study used starches with varying thermal and gelatinization properties and peanut protein as research objects, which investigated the effects of starch on the expansion structure, texture, color, rehydration, and rheological properties of peanut protein extrudates. In addition, the changes in starch structure (short-range ordered and long-range ordered structure) and protein structure (protein secondary structure, sulfhydryl group content, and disulfide bond content) during extrusion were also analyzed. The results showed that a value of starch-protein extrudates was significantly decreased (P<0.05). ΔE and b values were significantly increased (P<0.05). It also showed that the expansion structure, texture, and rehydration properties of peanut protein extrudates were closely related to the amylose content and thermal properties of the starch. Pea starch, which had a lower enthalpy (1.83 J/g), a higher amylose content (31.10%), and a lower gelatinization peak temperature (67.88 ℃), helped peanut protein extrudates form a porous expansion structure and improved the texture properties of peanut protein extrudates. For example, pea starch significantly increased the expansion ratio of peanut protein extrudates to 2.44, and reduced the density and hardness to 0.28 g/cm³ and 19.18 N, respectively (P<0.05). At the same time, the water holding capacity of pea starch- peanut protein extrudate (PASE) reached the highest in the experiment group (6.05 g/g), indicating that pea starch significantly improved the rehydration properties of peanut protein extrudates (P<0.05). In addition, the interaction between pea starch and peanut protein can promote the transformation of protein secondary structure from order to disorder, while the short-range ordered structure and crystal structure of starch are destroyed. The conversion of sulfhydryl groups to disulfide bonds increased the degree of protein crosslinking. Pea starch raised the viscosity, decreased the fluidity, and improved the elasticity of the extrudate system, according to rheological investigation. According to the above results, it can be seen that pea starch can effectively improve the expansion effect and quality properties of peanut protein extrudates, and this study provides scientific and technological support for the research of peanut protein extrusion and product development.