A new bio-polymer composite film of bacterial cellulose was biosynthesized by Acetobacter xylinum in static cultivation. The culture medium was mainly consisted of coconut water with sodium alginate as additive. Experimental results indicated that adding low concentration of sodium alginate in the culture could increase the yield very much. When the adding amount of sodium alginate in the culture medium was 4 g/L, the yield of the dried BC film was up to 8.35 g/L which is about 2.4 times of that of the un-additive system BC film. The properties of products were determined by FTIR, XRD, SEM and TGA. The products showed significantly changes in crystalline index and some difference in mechanical property compared with the control. And their water holding capacity decreased compared with the un-additive sodium alginate BC film.