Abstract: Based on geochemistry, sedimentary structure, trace element and rare earth element analyses for sandstone from Longli Formation in Sansui area of Guizhou Province, the provenance, mother rocks and tectonic background are summed up. It is inferred that the mother rock belongs to felsic and magnesian magma rocks which form in stable continental, partially form in volcanic arc and transition zone. It is proposed that the provenance might be derived from upper crust, the uplift basement belongs to stable craton, and the tectonic background is passive continental margin. Sedimentary structures and geochemistry data from Longli Formation reflectes a freshwater environment which correspond to the depression stage of rift basin extension.