The optimal extraction process of phytoglycogen(PG)from sweet corn by ultrasound-assisted method was studied,and the physicochemical properties and biological activities of PG were evaluated in this paper.The effects of solid-liquid ratio,ultrasonic power and ultrasonic time on the yield of PG were investigated and the process parameters were further optimized by orthogonal experiment.Furthermore,the physicochemical properties of PG obtained by ultrasound-assisted method were investigated.Meanwhile,the antioxidation,cytotoxicity,apoptosis and hemolysis of PG were evaluated in vitro.The results showed that the optimal extraction conditions were as follows:Solid-liquid ratio of 1∶9(g/mL),ultrasonic power of 160 W and ultrasonic time of 80 min,the actual yield was 14.31%±0.38%.The PG particle size obtained by ultrasound-assisted method was lower than that obtained by traditional water extraction and alcohol precipitation method.In vitro antioxidant experiment showed that PG had a certain antioxidant capacity,especially it was more sensitive to DPPH free radicals,and the clearance rate reached 54.58%±1.39%at 20 mg/mL.The results of biosafety evaluation showed that the survival rate of mouse fibroblasts(3T3)was higher than 95%after incubation with different concentrations of PG for 24 or 48 h.Meanwhile,PG had no obvious apoptotic effect on cells,and the apoptotic rate was lower than 7%at the maximum concentration.After 2 h of co-incubation,the hemolysis rate caused by PG on red blood cells was also much lower than the national standard(5%),which confirmed that PG had good biocompatibility with normal cells and red blood cells.Overall,this study showed that ultrasound-assisted method could improve the yield and physicochemical properties of PG,and also confirmed that PG was a non-toxic natural nanoparticle,which had great application potential in drug or food factor delivery.