Objective To construct sigF deletion mutant of Bacillus anthracis and the complementary strain of sigF deletion mutant in order to analyze the effect of losing sigF on formation of spores.Methods The spectinomycinadenyltransferase gene(spc) was inserted to replace sigF of B.anthracis by homologous recombination.A plasmid which contained sigF and sigF promotor was constructed and then transferred to the mutant to get a complementary strain of sigF deletion mutant.The characters of the mutant were analyzed by measuring growth curves, the ability of carbohydrate metabolism was compared, and spore formation was observed under a microscope.Results The sigF deletion strain A16D2△sigF was constructed from A16D2,which had a similar growth rate to the wild type A16D2 in logarithmic phase, but was not significantly different from the initial strain in the ability to use carbohydrates,although unable to form spores.The strain was found to maintain the state of asymmetric division by microfluidics experiment.Conclusion It is showed by this study that sigF is the essential gene of B.anthracis for spore formation, but not essential for vegetative growth.