This paper studies the relationship between wave velocity and rock brittle failure during the whole process of compression. The complete testing data for the stress-strain curve and the associated wave velocity-stress curve are obtained. The variation caused by internal cracking of the rock causes the corresponding variation of rock wave velocity

especially when the stress level reaches to 70%-80%. Based on the experimental results

it is shown that the stress at the critical point on the stress-strain curve is corresponded to that at the rapid deduced point on the wave velocity-stress curve

where the microcracks are rapidly growing. With the reducing of wave velocity

the travel times and discrete degree of S-wave and P-wave are sharply increasing. The amplitudes of S-wave and P-wave are reducing. However

the amplitude ratio between S-wave and P-wave is increasing. The Q values of S-wave and P-wave have a mutation phenomenon nearby the yield point of stress-strain curve. Considering the relation between wave velocity variation and stress-strain curve

this study shows that wave velocity and its characteristic parameters could be used as the sensitive parameter in the failure process. From this research

we can use the comprehensive information source to indentify the critical point of rock brittle fracture.