Abstract: Objective: To purify and characterize a water-soluble protein from Pueraria lobata and to fabricate its nanoparticles by heating-induced assembly. Methods: Pueraria lobata protein was purified by anion exchange chromatography High Q, and its molecular weight and amino acid sequence were determined by SDS-PAGE and N-terminal sequencing. The particle size, optical dispersion intensity and Zeta potential of protein nanoparticles were measured by laser-scattering particle analyzer. The drug loading efficiency of the nanocarrier was determined by chromatography. Results: A major water-soluble protein, named PP, was purified from Pueraria lobata and sequenced with a N-terminal amino acid sequence of DFVYDMCGNVLNGGTYYIL. PP was identified as a novel trypsin inhibitor by NCBI database searching and rypsin inhibitory assay. PP was also well-stabilized in the pH2~10 and 20~50 °C ranges. After heating PP solution (0.1 mg/mL, pH6.0) for 60 minutes at 100 ℃, homogenous nanoparticles (PP-NPs) were harvested. These PP-NPs had a particle size of 172.78 nm and a Zeta potential of −25.40 mV. The puerarin and berberine were effectively loaded onto PP-NPs, with loading efficiency of 33.83% and 24.61%, respectively. Conclusion: The major water-soluble Pueraria lobata protein PP can be fabricated into protein nanoparticles by heating-induced assembly, indicating a potential as drug carriers.