The invention relates to a laser ultrasonic detection system for quickly positioning faults and a detection method of the laser ultrasonic detection system. The system comprises a laser, wherein the laser is connected with a galvanometer scanning system and a controller; a scanning area is arranged on the lower end of the galvanometer scanning system; an air coupling sensor is arranged on the scanning area, and is connected with a four-way signal conditioning way module; the four-way signal conditioning way module is connected with a four-way high-speed A/D acquisition card; the four-way high-speed A/D acquisition card is connected with an upper computer software system and the controller; the controller is also connected with the upper computer software system and the galvanometer scanning system. According to the laser ultrasonic detection system for quickly positioning faults and the detection method of the laser ultrasonic detection system provided by the invention, the system datamemory space is reduced, the detection speed is improved, and the positions of the faults can be detected accurately.