The properties of a longitudinal guided wave with central frequency 5kHz propagating in partially grouted rock bolts were studied by experimental and numerical simulation methods. The guided wave was excited by the impact–echo method on the free end of the bolt, and the excited wave measured in the experiments was used as excitation input in the numerical simulation. The numerical results match well with the experimental ones. Two empirical formulas were obtained for when the reflected waves from the upper interface and from the embedded end of the bolt could be distinguishably detected. Conclusion is drawn from the simulation results that the guided wave energy velocity in the embedded section of the bolt increases with the increase of elastic modulus of the grout media. A new method was proposed for anchorage quality testing and its effectiveness was proved by a testing example.