The invention provides a construction method of long anchor rods for inverted arch treatment of a tunnel in a soft rock large deformation section. The construction method comprises the following steps: (S1) marking a plurality of construction rings in the longitudinal direction of the tunnel at an inverted arch part in the tunnel at a first interval, and marking a plurality of construction pointson each construction ring at a first annular interval; (S2) laying the long anchor rods on the construction points of each construction ring of the tunnel; (S3) injecting mixed slurry into the long anchor rods; and (S4) after grouting of the long anchor rods is completed for a first time period, installing anchor backing plates and nuts at the exposed ends of the long anchor rods. According to theconstruction method provided by the invention, the long anchor rods are laid to the inverted arch part of the deformation section of the tunnel according to requirements, and the soil body of surrounding rock of the inverted arch part of the deformation section is reinforced by grouting the long anchor rods, so that the soil body of the surrounding rock of the inverted arch part of the deformation section of the tunnel is stabilized, and it is ensured that the soil body of the surrounding rock of the inverted arch part after subsequent construction of the inverted arch part of the deformationsection of the tunnel cannot be deformed any more.