Measurements of the spectral dependence of diffraction efficiency (DE) of relief gratings which were formed on nanomultilayers (NML) As2S3-Se are described. Grating relief on the surface of samples was formed by direct one step laser writing. NML of the composition As2S3–Se  were prepared by computer controlled cyclic thermal vacuum successive deposition of two components from two separated boats (As2S3 and Se) on continuously rotated glass substrate at room temperature in one vacuum deposition cycle. The monitoring and determining of the total NML film thickness carried out during the thermal evaporation by 2 interference thickness sensors at λ=0.94µm in transmission mode.  A separate measurements of thiknesses of both components were carried out. Diffraction gratings with 1 μm period were recorded by two laser beams with s–s polarization (monomode DPSS green laser, λ = 532 nm and averaged power density spot 225mW/cm2) with synchronous diffraction efficiency measurement by red laser (λ = 650 nm) in first diffraction order. The intensity ratio 1:1 of recording beams was used in order to achieve maximum contrast of interference fringes. Direct one step grating relief formation by laser beam on the NML surface was realized. No additional wet etching was used. The depth value of the relief measured by atomic force microscope was 65nm [1].     The spectrophotometer СФ-46 (spectral range 190 - 1100nm) was modified to measure spectral dependences of DE. A non-polarised beam of light falled perpendicular the surface of NML. The arm with photodiode rotated around grating surface and perpendicular to the grooves to find the max value of current at given wavelength. Maximums of photocurrent corresponding to maximum of DE were registered in transmission mode vs. wavelength. The intensities of transmitted light through sample I0 and diffracted in the first order I1 at various wavelengths in the spectral region 550-1000 nm were recorded. Intensity of first order diffracted beam I1 and non diffracted I0 were used for DE calculations as I1 /( I0+2 I1)100%. First-order DE versus wavelength is shown on the figure.   The results show that the maximum values of DE of gratings recorded on the NML was observed at wavelength of 550nm. A feature of the spectral dependence is non-monotonic decay of DE in the spectral region. We suppose the observed variation of  relief gratings DE of NML structure can be associated with interference phenomena in a thin film. There are a different optical paths inside film for normally incident/ transmit Iо and angular passage of I1.     [