The purpose of this study was to fabricate composite nanoparticles using soy protein isolate (SPI) and sorghum bran arabinoxylan (AX) for the delivery of curcumin (Cur). The influences of AX concentrations on the physicochemical characteristic, stability and bioaccessibility of curcumin were investigated. The findings showed that the encapsulation efficiency of curcumin obviously increased upon incorporating AX in comparison to SPI-Cur particles. Hydrogen bonds and hydrophobic interactions were the primary driving forces for the formation of SPI-Cur-AX nanoparticles (SCA). SCA nanoparticles with 1.00 % AX exhibited a uniform size with orderly distribution, suggesting its remarkable physical stability due to the strengthened electrostatic repulsion. However, excessive AX led to aggregation of particles, a noticeable increase in size, and subsequently, a reduction in stability. Due to the heightened free radical scavenging capacity of sorghum AX, SCA nanoparticles exhibited superior antioxidant capabilities. Compared to free curcumin, encapsulation within composite particles significantly enhanced the retention rate and bioaccessibility of curcumin. This improvement was attributed to the potent emulsification ability of AX, which coordinated with bile salt to promote the transfer of curcumin into micelles. The research provides an effective strategy for developing food-grade delivery carriers aimed at enhancing dispersibility, stability and bioaccessibility of the fat-soluble bioactives.