In this research, flax seed mucilage was extracted. Composite film of sodium alginate and flax seed mucilage was prepared. Norbixin pigment and tungsten oxide (WO3) nanoparticles were used to modify the film structure. The color, crystallite, thermal and mechanical properties of the films were investigated. Also, the antibacterial properties of the prepared films against Escherichia coli and Staphylococcus aureus bacteria were investigated. The obtained results showed that the pure alginate/mucilage film does not have very high transparency, which is reduced by adding tungsten oxide nanoparticles and norbixin pigment. The effect of tungsten oxide nanoparticles in reducing film transparency has been greater than that of Norbixin. Examining the factor a (green-red) shows that this factor has increased with the increase of Norbixin and tungsten oxide nanoparticles. Examining factor b (blue-yellow) shows that with the increase of Norbixin and tungsten oxide nanoparticles, this factor has increased. By examining the XRD spectrum of the pure alginate/mucilage film, it was found that this film showed two broad peaks at 2θ of 10° and 20°, which indicates the relatively amorphous structure of this film. In the alginate/mucilage film modified with tungsten oxide nanoparticles, the peaks related to the crystalline nanoparticles in 2θ of approximately 25, 30, 35, 40, 50, 55 and 65 degrees are quite clear, which shows that these nanoparticles improve the crystalline structure of the film. By examining the TGA curves of the films, it was found that the addition of tungsten oxide nanoparticles and norbixin pigment increased the thermal stability of the film. Examining the antibacterial property of the films showed that the addition of tungsten oxide nanoparticles and norbixin pigment increased the antibacterial property of the film significantly (p<0.05).