Degradable polymer drilling fluid

The invention relates to a degradable polymer drilling fluid, and belongs to the technical field of coal bed gas drilling well horizontal well exploitation application. The degradable polymer drilling fluid is characterized in that the degradable polymer drilling fluid comprises water, a degradable densifier, a water-based lubricant, a water blocking resistant agent and an alkalinity adjusting agent, wherein the weight percentages of the degradable densifier, the water-based lubricant, the water blocking resistant agent and the alkalinity adjusting agent respectively account for 1-1.5%, 1-3%, 0.5-1.0% and 0.1-0.2% of the weight of water. The degradable polymer drilling fluid can be used for drilling coal bed gas horizontal wells, can effectively stabilize the coal bed well wall and improve the cuttings carrying capability, and also has the characteristics of degradability, furthest protection of the coal bed, strong coal bed well wall stabilizing capability, good nicking carrying and lubrication capabilities,