Abstract: This paper studied the effects of agar on spontaneous mutation of Komagataeibacter xylinus,bacterial cellulose(BC)productivity and BC structure in static and shaken-flask culture. The rate of mutation was measured by plate counting. BC productivity,crystallinity,and polymerization of degree were determined by weighing method,Fourier transform infrared spectroscopy(FTIR)and viscosity method,respectively. Meanwhile,the cellulase activity was assayed by spectrophotometry. The results showed that there were mutants in both static and shaken cultures and the yield of BC was 0.16 and 0.09 g/L,respectively. No mutant strain was found in the static culture with 0.05% agar and in the shaken culture with 0.10% agar. BC yield increased to 0.38 and 0.34 g/L,respectively. No mutants were detected in nine times of transfer passages of the static culture with 0.05% agar. However,the mutants appeared in the second transfer passage of shaken culture with 0.10% agar. Compared with that of BC in the static culture,0.05% agar added into static culture decreased the degree of polymerization and crystallinity of BC by 4.0% and 12.9%,respectively.0.10% agar in shaken culture decreased the crystallinity of BC by 51.2%.Although the activity of cellulase was not affected by culture method and agar,BC with lower crystallinity in the shaken culture with 0.10% agar was more hydrolyzed by the cellulase,resulting that the degree of polymerization of BC decreased by 42.2%.