The invention belongs to the technical field of coal-bed gas resource exploitation and provides a construction method for reinforcing a coal-bed gas well penetrating through a goaf by virtue of small guide hole grouting. According to the method, the problem that during passing-through of a fracture zone or a caving zone of the goaf, safe drilling construction fails to be conducted due to the mud loss is solved. A second spud-in drilling construction process is adopted; when second spud-in drilling is conducted through the fracture zone and the caving zone of the goaf, a small guide hole is constructed firstly; then grouting is conducted on the small guide hole, and thus a cylindrical grouting reinforced area closing fractures around the small guide hole is formed; and second spud-in drilling continues to be conducted. Drilling construction of the coal-bed gas well in the goaf is conducted through the method so that it can be guaranteed that the coal-bed gas well is safely and smoothly drilled in a broken rock stratum of the goaf, and the overall stability of well wall surrounding rock of the coal-bed gas well can be greatly strengthened.