The five step Tessier sequential extraction method and the infrared spectroscopy technology were used to investigate the changes of chemical forms of Cu in soils infected by Cohnella sp., meanwhile, the possible mechanism of changing forms of Cu was studied. Results showed that a week after soil was infected by different inoculation of Cohnella sp., pH values of soil solution reduced, distribution ratio of exchangeable form and organic combined form of Cu increased, and acid soluble form, oxidation form and residual form of Cu redued. The changes of the exchangeable form, oxidation form and residual form of Cu were influenced by pH values ; while, the increase of organic combined form of Cu was related to the amount of Cohnella sp. and low molecular weight organic acids produced by microbial metabolism. So, the Cohnella sp. could change the chemical forms of Cu in soils in Xinqiao Mining Area, and substantially increase bioavailability of Cu in soils.