Curcumin (Cur) has antioxidant, anti-inflammatory and other biological activities, but its poor stability, low water solubility and other defects limit the application. Herein, Cur was nanocomposited with soy isolate protein (SPI) and pectin (PE) for the first time and its characterization, bioavailability and antioxidant activity were discussed. The optimal encapsulation process of SPI-Cur-PE was as follow: the addition amount of PE was 4 mg, Cur was 0.6 mg and at pH of 7. It was observed by SEM that SPI-Cur-PE were partially aggregated. The average particle size of SPI-Cur-PE was 210.1 nm and the zeta potential was −31.99 mV. Through XRD, FT-IR and DSC analysis, the SPI-Cur-PE was formed through hydrophobic interaction and electrostatic interaction. The SPI-Cur-PE released more slowly in simulated gastrointestinal treatment and displayed higher photostability and thermal stability. SPI-Cur-PE, SPI-Cur and free Cur had scavenging activities for 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radicals.