In this work,an asymmetry waveguide photoconductivity is demonstrated for composition-graded CdS1-xSex nanobelt[1].Via changing the excitation position from the wide-bandgap(CdS0.95Se0.5)to the narrow–bandgap(CdS0.55Se0.45),the current-voltage character of the nanobelt shows obvious asymmetry,with the photoconductivity for the excitation position on CdS0.95Se0.5 is higher than the photoconductivity for the excitation position on CdS0.55Se0.45 [2].With positive or negative bias,the device show different spectral response.