The law of guided wave propagation in grouted and free rock bolts is studied by theoretic analysis and laboratory testing method. The wave propagation velocity in grouted rock bolt and free bolt within 20 kHz-3 MHz is tested in laboratory respectively. The and research shows that the different frequencies have different sensitivities to grout quality. Low frequency (20 kHz-200 kHz) guided wave changes its velocity greatly with grout quality; and high frequency (1-3 MHz) doesn’t change. So low frequency (20 kHz-200 kHz) which has high sensitivity to grout quality can be used to test grout quality and high frequency (1-3 MHz) whose velocity doesn’t change with grout quality can be used to test integrity of rock bolt. The laboratory test results show that the method has very good accuracy; and a method for testing grouted length of rock bolt is proposed