The invention provides a construction method for improving grouting quality of hollow anchoring rods in a tunnel anchor. The method is applicable to the technical field of building construction and includes the following steps that perpendicular drilling is conducted on a rock surface within a certain depth scope through a pneumatic rock drill to form anchoring rod holes; hole expansion construction is conducted from the hole openings of the anchoring rod holes to the inside within a certain depth scope through a pneumatic pick; the pneumatic rock drill adopts hollow threaded rods for drivingone end of each anchoring head and venting pipes into the anchoring rod holes, and the anchoring heads and the venting pipes are firmly bound; gaps around the hollow threaded rods are filled with an anchoring agent; fast-setting gypsum adhesive cement is used for fully sealing expanded holes; after the segments sealed by the anchoring agent and the fast-setting gypsum adhesive cement are solidified, the hollow threaded rods are sleeved with padding plates from the tail ends, and nuts are used for tightly locking the padding plates on the surface of the solidified fast-setting gypsum adhesive cement; a grouting machine is adopted for conducting high-standard grouting construction according to parameter requirements. By means of the method, not only can design requirements be met, but also the cost can be reduced to the greatest degree, the actual operation performance is great, and the construction difficulty of rigid grouting of the tunnel anchoring rods is effectively solved.