Recycling gas drilling is a new drilling technology.This paper can be divided into three parts,with the purpose of introducing and analyzing the characteristics of this new technology.First,the major equipment characteristic of this technology was introduced.Secondly,compared with conventional gas drilling,Angel's model was used to analyze the wellbore flow characteristics.Due to the closed loop and the effect of back pressure caused by the equipment,the gas flow rate decreases dramatically during drilling.Apart from this,it is also found that the kinetic energy at the casing shoe is always smaller than that at the top of the collar.The proposing of the drilling limit concept points out the basic difference between the two gas drilling technologies.Lastly,according to the results of the theoretical analysis,gas supplement operations for the wellbore must be conducted.Thus,two gas supplement schemes are presented in this paper,to provide some guidance for field operations.