The structure and properties of nano-MnO2 chitosan composite film were analyzed to provide reference for the preparation of biodegradable packaging materials. The KMnO4 was combined with MnSO4 to form nanometer manganese dioxide (nano-MnO2) by hydrothermal. Then, nano-MnO2-CS composite film was successfully prepared through CS and nano-MnO2 in a mixed solution of acetic acid and glycerin under ultrasonic wave. The properties of the composite film, such as tensile strength, elongation at break, oxygen and water resistance, light transmittance and antibacterial property were investigated. The structure was characterized by Fourier transform infrared spectroscopy, X-ray powder diffractometer and the digital polarizing microscope. The thermostability was studied by thermogravimetric analysis. The nano-MnO2 was uniformly dispersed in the chitosan and they were connected to each other by strong intermolecular forces. When the mass ratio of nano-MnO2∶CS is 1∶5, nano-MnO2-CS composite membrane has excellent oxygen and water resistance, strong light barrier performance, good flexibility, thermal stability and antibacterial property. Therefore, the prepared nano-MnO2-CS composite film has improved mechanical properties and barrier properties, enhanced thermal stability, and has a certain antibacterial effect.