Abstract: Polymer drilling fluid for CBM horizontal well collapse causes serious pollution of coal seam in the stability of shaft wall, which needs to post gel breaking technology to remove pollution. Relative to the oil and gas wells, gel breaker for coalbed methane wells has the characteristics of slow gel breaking speed and more residues for easily damaging coal seam. Based on this, the selected appropriate seam breaker JBK can degrade polymer drilling fluid completely under the condition of adding 1% gel breaker in 2 hours with fast and downright gel breaking in low temperature and no residue. Indoor core flow experiment results show that the gel breaking liquid can improve coal seam and effectively remove the pollution of coal seam caused by polymer drilling fluid. In the site construction, by adopting the combinated gel breaking construction technique of surface cleaning and deep plugging and removing, we get good construction effect, which successfully applies in gel breaking operations of 6 U wells.