Some basic princip les of the techniques of optical fiber time delaywere analyzed theoretically, aswell as its applications on the laser directional detection warning systemswere studied experimentally. A high speed digital filtering was adopted in the experiments to filter the disturbed signals. Then the angle of incidence of laser radiation is calculated bymeasurement of the op tical fiber delay time of the laser energy barycenter. Thereby, the ratio of false alarms in the laserwarning systems was reduced greatly. The accuracy and stability of the delay directional detection are improved significantly.