The invention discloses a tunneling method capable of weakening hard rock strength. According to the method, a tunneling machine, an integrated grinding jetting drilling machine with the tunneling machine as a carrier, and a high-pressure water pump are arranged on a tunneling working surface; the integrated grinding jetting drilling machine is adopted to form drilled holes in a rock body, and a series of conical crack clusters are formed through cracking cutting on the basis of hole drilling; a high-pressure hole sealing device is used for sealing the tunneling surface for a distance, the high-pressure hole sealing device is communicated with a high-pressure water pump through a water inlet pipe, the characteristic that the rock body is resistant to pressure but not resistant to drawing is utilized, the conical crack clusters in the rock body are expanded to form a dense conical crack net, and therefore the rock strength is weakened; a tunneling machine cutting head is adopted to cutthe rock which has an internal conical crack net, the tunneling efficiency is greatly improved, the service life of the tunneling machine can be prolonged, and the tunneling cost is reduced.