Abstract: The glass fiber reinforced plastic oil gathering pipeline in an oil field failed due to leakage. The causes of pipeline leakage failure were analyzed by means of macro observation, size measurement, glass transition temperature test, resin content test and micro analysis. The results show that under the action of bending stress or composite load dominated by bending stress, the stress at the stress concentration of the joint (at the root of external thread) exceeded the ultimate stress that the material can bear and transverse fracture occurred. This stress mainly came from stratum settlement and other external forces.