The horizontal wellbore plays an important role in drilling for coal bed methane (CBM) all over the world. It is the quality of the horizontal wellbore drilled in the coal measure which plays a significant role in CBM collection efficiency. It can also improve coal extraction safety as it lessens unintended drilling deviations. This paper analyzed the deviation factors and conditions of the horizontal wellbore, the developing tendency, the deviation stress state, and also the critical control factors of the horizontal borepath. Finally, the geometric models for the maximum deviation, the optimum decision point, and the rotational angle for automated correction were established to develop a quadrant orientation algorithm of automated correction. Through integrating this algorithm and the hydraulic correction technology that was proved by theoretical analysis and practical experiment, a new hydraulic correction drill tool that doesn't require a traditional drill bit hoisting (DBT) or signal transmission has been developed and tested by manufacturing its circuit board and performing a computer simulation. (C) 2010 Elsevier B.V. All rights reserved.