Abstract: Based on the data of systematic chemical analyses, the transformation between the non-marine facies in the Permian system of the Chaohu Lake, Anhui Province are discussed paper, with the application of MnO/TiO₂ ratio. The results obtained are basically consistent those from C/S ratio, ¹³C,as well as the synthetic analyses of palaeontology and the sedimentary vironmcnt of petrostratigraphy. Therefore, it is in evidence that MnO/TiO₂ can be regarded as fective geochemical index for defining the depositional cnvironment of marine sediments and is available for studying on the changes between marine and non-marine facies.