A staring laser threat detection system based on Michelson interferometer is designed, and rules of orientation direction precision and filter’s transmission efficiency are analysed in theory. Results show that, round interference stripes are formed when input laser is transmitting through the laser threat detection system, the direction and wavelength of input laser can be calculated based on the central coordinate and space of stripes.The direction precision is decided by the ratio of focal lengths of varying lens and spherical reflector when the pixel size of detector is fixed , and the precision rises when the ratio decreases. Filter’s transmission efficiency is decided by focal length of varying lens. If the varying lens’s focal length is ten times of fish eyes lens’s focal length, filter’s transmission will be 90.0%～87.5% for inputing laser with angle from 0°～90°, and this can make the detecting system have high sensitivity for every input laser from 0°～90°.