In the last few decades, a Significant advance in the laser detection techniques have occurred in a civilian application like optical fiber communication system, lidar system and now satellite communication in the aerospace and a military application, one of the most applications in military is the laser guided missiles and bombs encountered high development and formed high threat for strategic and special targets. The development of a laser warning system (LWS) is essential to detect the laser guided weapons attack. A classic LWS is composed of an optical subsystem, laser detector, and processing unit. The design of a LWS is constrained by the cost, optical system size, detector type, and the required processing operations. In this paper, a 15-degree field of view optical subsystem, diffraction grating, and a sky camera is used to reduce the whole system size, reduce the cost, and decrease the number of false alarms initiated by the dark current on the classical detectors. The optical subsystem is designed to shape the laser spot diameter to be 350µm to avoid detection saturation. The design and fabrication of the optical system guaranteed a signal-to-noise ratio up to 175dB in a clear atmospheric condition. This LWS outperforms the state-of-art LWSs in laser guided weapon detection.