In order to detect both direction and wavelength of attacking incident laser beam, a wide-angle staring laser threat detection system based on grating diffraction is designed, analytic expressions of laser direction and wavelength are deduced, and imaging rule of the system is analyzed. The detecting ability of the system is put to test by utilizing 1064 nm pulse laser. Results show that incident laser beam is imaged to three equal-interval bright spots by this detection system, and the direction and wavelength of incident laser can be calculated based on the coordinate of middle spot and the interval of two adjacent spots. Optical aberration of fish-eye lens makes the system′s imaging spots larger, more blurred and distort to cone with increase of incident angle of the laser beam. Half angle of vision of the designed system is 35°, and both direction and wavelength of incident laser beam can be detected effectively with the maximum detection errors of 1.5°and 60 nm, respectively.