Abstract: The glass fiber reinforced plastic pipe used in ground gathering system of an oil field in China leaked during pressure test on site. The failure reason was analyzed by macroscopic morphology observation, wall thickness measurement, glass transition temperature test, resin content test, hydrostatic pressure test, short-term failure pressure test and microscopic morphology observation. The results show that by the external force dominated by the bending stress, a large number of circumferential cracks appeared in the thickened transition region of the glass fiber reinforced plastic pipe outer wall, resulting in the reduction of overall internal pressure resistance of the pipe, and leading to the leakage of the pipe during pressure test on site. The glass-transition temperature of outer surface of the glass fiber reinforced plastic pipe was low, indicating that the curing degree of the outer surface was low and the performance was poor. The poor performance promoted the appearance of circumferential cracks in the outer wall of the pipe.