The relationship between processing conditions and specific chemical reactions led to film growth in plasma is identified by optical emission spectroscopy to simplify the optimization process of film properties. SiH* transient behavior after plasma ignition in parallel plate silane/germane/hydrogen plasma is investigated with the variation of germane, hydrogen flow rate and power. The effect on interface property between p layer and intrinsic layer in amorphous silicon germanium solar cell is obtained. H-alpha*, H-beta*, SiH* and GeH* emission intensity is recorded when germane and silane/germane flow rate changes. Ge content is analyzed by optical band gap and Raman spectra of amorphous silicon germanium films. The results are expected to serve as a guide for improving the performance of solar cells.