In this paper,Fraunhofer diffraction of sinusoidal grating aroused by random incidence laser is studied.Distribution of relative light intensity is analyzed.Relationship between bright stripe′s location and incidence laser′s information is studied and width of the bright stripe is also discussed.Formulas are deduced to find out the incoming laser′s wavelength and direction by inputting the location of the bright stripes.Based on the theoretical analysis,design of a prototype device is put forward.The scheme uses a CCD to observe the diffraction pattern,a DSP to sample the transfer the image information and a SCM to process the data.The performances of the prototype are given out with the parameters of the components and units.