Abstract: Gas drilling is a practical drilling technology arises in recent years. It had been applied to protect pay formations, increase drilling speed, decrease well construction time and deal with circulation loss. Gas drilling is one way flow and is used to take along cuttings and clean borehole with compressed air. Current logging monitoring system can't meet the need of gas drilling and many problems occurred compared to mud drilling, such as BHA failure, downhole burst, formation water producing and borehole wall sloughing. The paper had carried on the monitoring while drilling research based on downhole burst theory and monitoring technology so that UBD gas monitoring system and matched analysis technology were formed. Then detailed monitoring service description about the GMWD technology in many wells was provided. It is verified that the GMWD technology is reasonable and practicable and can provide a safe downhole environment for gas drilling.