Abstract: Experiments were conducted in a pilot-scale gas-lift loop reactor with an upleg measuring 10 cm in diameter and 3.21m in height. The gas holdup at different gas injection rates and liquid recirculating velocities foreleven different liquid gas systems were measured, and the data correlated. The results yielded the correlation ε =0.647 for low-viscosity liquid systems. With the above correlation and a simplified momentum equation for fluid flow in the loop, the gas holdup and liquid recirculating velocity for a given gas injection rate in a given loop may be predicted by calculation, with an average deviation of ±3.2% and ±4.6% for ε and uL respectively.