In this article,we report another form o f photoreflectance spectroscopy-space differential photoreflectance (SDPR) spec troscopy.SDPR has the same mechanism with PR but has better signal-to-noise ra tio and sensitivity.SDPR and PR spectra for GaAs/AlGaAs quantum wells are obtained.Experimental results show that the SDPR spectrum has ample spectrum st ructures. -