Abstract: For the problem of low success rate in the communicating operation of CBM horizontal well drilling operations using MWD, the rotating magnetic locating tool, MTS, was developed, which can supply powerful supplement and calibration for MWD measurement within a certain distance. The paper described the technical process and role of the communication. Beginning with the measuring principle of MTS, the measurement errors of the two tools were compared in three aspects: measurement lagging, working style, and error propagation and error ellipsoid. Field examples of the successful application of MTS in the CBM connectivity operations were described. The result can be obtained that different measurement principle and different working way cause different error propagation, thereby lead to the difference on measurement accuracy and communicating job success rate.