Abstract: EM-MWD technology has limited signal transmission efficiency during gas drilling,because of a high degree of interference from complex strata,rapid signal attenuation,and poor noise-resistance capacity.To solve the problems,MMWD technology would be used because it can use the drillstring as a microwave waveguide to use the MWD for parameters and signal transmission during the gas drilling.Based on the study of the high frequency wave transmission characteristics and the main influencing factors of microwave transmission along the string,the selected microwave frequency was verified,and eight wave types that could propagate along the string and their attenuation coefficients were obtained.After completing that phase,the MMWD prototype and supporting control and processing software were developed.The prototype was tested several times in Well YL-x of the Yuanba Gas Field in Sichuan,and the fault-free operation duration for one run reached 120.0 h,and the total operation time reached 234.0 h.The maximum measured depth exceeded 3 000.00 m,and the measured and transmitted downhole temperature data generally conformed to the ground temperature distribution law;the well inclination was in consistence with the wire-logging inclination.The study showed that MMWD technology could solve the problem of limited measured depth of EM-MWD technology,and had accurate and reliable measurement results,which provided a new high-efficiency MWD method for gas drilling.