Abstract: To investigate the effect of Piriformospora indica on drought resistance of Nicotiana tabacum, a pot experiment was conducted by using polyethylene glycol (PEG) 6000 to simulate drought and the malondialdehyde (MDA) and proline contents, relative electrical conductivity and expression levels of drought-related genes in tobacco leaves under drought stress were analyzed. The results showed that P. indica could colonize in the roots of N. tabacum and promote the growth of both root and shoot of the plants. When P. indica-inoculated plants were under drought stress, the symptoms of water shortage were slighter, the proline content in leaves was significantly up-regulated, while the MDA content and relative electrical conductivity of leaves were significantly decreased comparing with those of un-colonized treatment. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that the relative expression levels of drought-related genes RD29A, ERD10A, RD26A, SDIR1, HAT, ERD1 and DREB2A were higher in leaves of colonized plants under drought stress. P. indica enhances the drought resistance of N. tabacum via reducing tobacco cell biological membrane damage degree, enhancing the antioxidant ability of tobacco, promoting the accumulation of osmotic substances proline and up-regulating the expression of drought-related genes.