A model machine of super wide angle laser warning system based on grating diffraction was developed，and the sensitivity estimate-formula of the system was derived，then the minimum detectable energy density of the machine was tested by using 1064nm pulse laser in the half field angle range 0°~78°.Results show that the grey value of imaging light spot in this warning system decreases from 20 to 7 when the incident laser energy intensity remains 1.8 nJ/cm2 in the angle scope of 0°~42°，and the minimum detectable energy density increases from 2nJ/cm2 to 7nJ/cm2 with the incident angle from 48°to 78°.With the incident angle increasing，the optical aberration of the system increases，it causes the imaging spot to be bigger.That is the main reason for the increasing of the minimum detectable energy density.