Abstract: The relationship between Ge content of Si_1-xGe_x layers and growth conditions was investigated via UHV/CVD system at relative low temperature of 500℃.Si_1-xGe_x layers were in a metastable state in this case.10-period strained 3.0 nm-Si_0.5Ge_0.5/3.4 nm-Si multi quantum wells were obtained directly on Si substrate.Raman Measurement,high resolution electron microscopy and photoluminescence were used to characterize the structural and optical properties.It is found that such relative thick Si_0.5-Ge_0.5/Si multi quantum wells are still near planar and free of dislocations, that makes it exploit applications to electrical and optical devices.