In this paper, we introduce a rotational through-transmission ultrasonic propagation imaging system to inspect the full thickness of the entire cylindrical section of filament-wound composite overwrapped pressure vessels. This system can achieve high signal-to-noise ratio throughout the cylindrical section of pressure vessels by using a rotational scanning method. Based on the advantages of the laser ultrasonic system that can generate and detect ultrasound waves by using a small-diameter laser beam and making an inspection path in a narrow environment, this system directs the laser beam inside the pressure vessel via a mirror to enable the through-transmission mode for vessel inspection. A type-3 pressure vessel was inspected using the system developed, which successfully detected two impact damage spots and showed the filament winding direction clearly. The test results show that the system developed is highly reliable and can replace the current hydrostatic sample test for pressure vessel safety certification.