The work aims to study the effects of ultrasonic-microwave synergistic treatment on nanocellulose-starch film, so as to prepare better functional packaging film and expand application of nanocellulose-starch packaging film. CSNC-CSS film was prepared by corn straw nanocellulocellulose (CSNC) and corn straw starch (CSS), and the effects of different ultrasonic-microwave co-treatment systems on the properties of CSNC-CSS film were investigated. Compared with CSNC-CSS film prepared by other methods, CSNC-CSS film prepared by ultrasonic-microwave synergic system had better properties. The tensile strength of the film increased from 14.92 MPa to 26.46 MPa, with a growth of 77.35%. The elongation at break increased from 64.75% to 90.08%, with a growth of 39.12%. After ultrasound-microwave treatment, the moisture permeability and oxygen permeability decreased by 25.57 and 41.45% respectively. The light transmittance and dissolution time increased. CSNC-CSS film after ultrasonic-microwave synergistic treatment has better mechanical properties, moisture resistance and gas resistance, and has broad market application prospect.