Abstract: To locate the enemy laser source in omni-directional laser warning based on diffuse reflection detection based on geometrical optics principles and machine vision concepts, this paper introduced 8 unknown parameters including R, , , d, , , , to describe the spatial position relationships among enemy laser source, the laser spot radiated on one flat plane and our omni-directional laser warning fisheye lens in typical battlefield environment, deduced the analytic expression of the laser spot contour on image surface, and acquired the 8 parameters from the spot coordinates data on image surface. Thus the spatial position relationships were obtained, the enemy laser source was located, and laser warning was achieved. The experiment result verified the feasibility of the omni-directional laser warning devices.