peanut protein was fermented by Lactobacillus pentosus, to study the effects of different protein composition of peanut protein isolate, arachin and concomitant arachin on their molecular structure and thermal properties during fermentation, the composite gel was prepared by compounding peanut protein with myofibril protein, the rheological properties of the composite emulsion and the texture properties of the composite gel were studied to reveal the molecular mechanism of the effect of L. pentosus on the gel properties of peanut protein. The results showed that the free sulfhydryl content, surface hydrophobicity and denaturation temperature of arachin were increased, β-sheet content and denaturation enthalpy were decreased by L. pentosus fermentation. It can reduce the content of free sulfhydryl group, surface hydrophobicity and denaturation enthalpy of peanut protein isolate and concomitant arachin, the denaturation temperature and α-helix content of peanut protein isolate and arachin were significantly increased. After fermentation, the structure of arachin developed to the maximum and the thermal stability of arachin was higher, which proved that L. pentosus could promote the gel modification of peanut protein. The complex gel formed by fermentation with arachin is easier to form porous structure and has better macro-elasticity than the complex gel prepared by modification of arachin and isolate protein.