The influence of existing cracks on acoustic emission (AE) wave propagation characteristics is not taken into account when using AE technology to locate cracks or detect damages in concrete structures, which often leads to large deviations in detection results. To explore the influence of crack parameters on the velocity and amplitude attenuation of AE wave in reinforced concrete (RC) slabs, four-point static loading test and AE test were carried out on three RC specimens with different protective layer thicknesses, and the influences of crack depth, crack width, and crack amount on the propagation properties of AE wave were analyzed. Tests and analysis results show that crack width and crack amount both had little effect on the velocity and amplitude attenuation of AE wave, while crack depth had significant effect. With the increase of the crack depth, the amplitude attenuation increased, and the velocity decreased. Then, a time-of-arrival location method based on variable velocity was proposed considering the effects of cracks, which was compared with traditional method in detecting crack locations. Results indicate that the proposed method had higher accuracy in detecting crack locations in RC structures.