Abstract: In order to find out the effects of Microbial agent MP(Bacillus magaterium)spraying on the quality of tobacco leaves, two-dimensional gel electrophoresis(2-DE)was used to analyze the differences of protein expression between tobacco leaves sprayed with MP and water respectively. The results revealed that the expression levels of six proteins changed significantly, among them the expression levels of five protein points increased, and that of the other one decreased after MP treatment. The six differential proteins were identified with matrix-assisted laser desorption ionization time of flight mass spectrometry(MALDI TOF/TOF MS), the results showed that four of them were recognized as tobacco acidic chitinase PR-P, tobacco chitinase precursor, endochitinase A precursor and osmotin respectively. Chitinase and osmotin closely related to plant's disease resistance, it indicated that the emergency system against exogenous bacteria might be induced and by which disease resistance was improved after MP spraying.