Abstract: A preparation method of flexible transparent radiation shielding film based on bismuth compounds and its application are provided, in which bismuth compound nanoparticles, polyvinyl alcohol and trace glycerol are mixed to produce a flexible transparent radiation shielding film. The invention disperses the nanoparticles in water to form a stable dispersion, which ensures the homogeneity of the sol obtained by mixing the nanoparticles with polyvinyl alcohol. This invention avoids the decrease in transparency of the composite film as induced by agglomeration of the nanoparticles, achieving a light transmission of over 70% in the visible wavelength band (400-800 nm). With the aid of trace-mount glycerol, the film features long-term stability and flexibility. Importantly, the lead-free film shows a high shielding ability from the medical X-ray band (10-100 keV), which is comparable to Cu foil of identical thickness.