Existing laser warning based on the diffraction grating has the following disadvantages. The diffraction efficiencies of ±1 order based on sinusoidal grating are low and the diffraction efficiencies of -1 order and 0 order based on blazed grating are very low. These shortcomings have reduced the reliability of the laser warning. A method for improving the blazed grating was presented. The two blazed gratings inverted docking, some no grating space was vacated in the middle of the grating. This improvement can increase the diffraction efficiencies of -1 order and 0 order. This grating will effectively overcome the missing alarm. The improved blazed grating was designed and processed with blazed wavelength λ=800 nm. The diffraction efficiencies of 0 order and ±1 order were derived. This grating was tested by two-dimensional laser warning using the laser with λ=808 nm and λ=850 nm. When wavelength of the incident light close to the blaze wavelength, the experimental results show that the improved blazed grating diffraction efficiencies of -1 order and 0 order have greatly improved, and they can be effectively detected by CCD. The reliability of two-dimensional laser warning is improved using this improved blazed grating.