Diagnosis and resolution faults of gas bearing turbo- expander influences the operation of refrigeration system.Through the analysis of the structure of gas bearing turbo- expander is of great importance for fault diagnosis. Crashes,caused by the rotor imbalance,was eliminated by static balance and dynamic balance test,when gas bearing turbo- expander was started and run,it should be regulated not to overspeed to ensure that rotor were not overloaded. The reason of gas bearing stability was analyzed,caused by the radial load and frequent start-stop and flash power outage. The relationship between gas supply pressure,radial clearance and the rotor balance was analyzed. Clearance,between the machine shell and wheel,could be adjusted to avoid the increase of the internal leakage. Measures was adopt to reduce external leaks,such as adjusting the sealing gap at the back of the wheel and providing plenty of sealing gas. The causes of liquid impact fault was analyzed,and processing method was put forward. Failures caused by gas pipeline jam and unclean bearing gas were analyzed. Methods are proposed to ensure safe and stable operation of the turbo- expander gas bearing,such as rigorous test of dynamic and static balance,the correct assembly,standardized operation,and regular maintenance.