An airborne infrared laser leak detection technology is proposed to detect natural gas pipeline leakage by helicopter which carrying a detector that can detect a high spatial resolution of trace of methane on the ground. The principle of the airborne infrared laser leak detection system is based on tunable diode laser absorption spectroscopy. The system consists of an optical unit including the laser, camera, helicopter mount, electronic unit with GPS receiver, a notebook computer and a pilot monitor. And the system is mounted on a helicopter. The principle and the architecture of the airborne infrared laser leak detection system are presented. Field test experiments are carried out on West-East Natural Gas Pipeline of China, and the results show that the airborne laser leak detection method is suitable for detecting gas leak of pipeline on plain, desert and hills but unfit for the area with large altitude diversification.