Method for developing coal bed gas by deeply penetrating radial horizontal well by hydraulic power

The invention provides a method for developing coal bed gas by deeply penetrating a radial horizontal well by hydraulic power. The method is used for a well for forming a production casing by casing cementing. The method comprises the following steps of: step 1: putting down a guide device (9) and positioning; step 2: putting down a milling drill bit (13) and drilling a guide hole with a pre-set diameter on the production casing; and step 3: putting down a jet spraying nozzle (15); self-propelling the jet spraying nozzle (15) to a target coal bed under the effect of a high-pressure water jet after the jet spraying nozzle passes through the guide hole of the casing to form a horizontal hole with a pre-set diameter and a pre-set depth. Therefore, a coal bed gas exploiting channel is established and the requirements of the exploiting rate of the coal bed gas are met.