The invention discloses a shale gas horizontal well geosteering method. The method includes following steps: according to lithological and electric characteristics of a target stratum, performing stratigraphic division on the target stratum, and determining and contrasting a marker stratum; on the basis of three-dimensional after-stack time migration and pre-stack time migration data, utilizing a Geoframe interpretation system for human-computer interactive interpretation in a workstation, and performing precise tracking contrast on the target stratum to realize morphological structure of each stratum; adjusting A target track; geosteering a horizontal section, wherein in the process of real drilling of the horizontal section, stratum inclination angle along a track direction usually changes, while drilling data need to be collected timely, a gas stratum and the marker stratum to determine current real drilling position, track needs to be monitored in real time, prediction needs to be performed in advance, and directional construction needs to be guided to ensure the drilling track to pass within a designed stratum range. The shale gas horizontal well geosteering method is simple to operate, easy to master and needless of special professional instrument and equipment.