The invention discloses a grouting method for a drilling rod and belongs to the technical field of drilling. The grouting method is characterized by comprising the following steps: a, connecting the upper end of a back pressure valve with the drilling rod, and connecting the lower end of the back pressure valve with a drilling tool; b, tripping the drilling tool and the back pressure valve in a well, enabling slurry in the well to reflux into the drilling rod from bottom to top by a self-grouting channel of the back pressure valve, and finishing automatic grouting of the drilling rod; c, positively circulating the slurry, downwards moving a piston in the back pressure valve to block a slurry reflux groove hole and closing the self-grouting channel. According to the grouting method disclosed by the invention, reverse spraying of the slurry in the well can be prevented and the slurry in the well is enabled to automatically reflux into the drilling rod, and the operation that the grouting device is connected and pours the slurry into the drilling rod once a part of the drilling rod is laid down is not needed, so that the workload is greatly reduced, and the grouting cost is effectively reduced.