Abstract:A new method for measuring in-situ stresses with ultrasound is developed based on acoustoelasticity theory. First,acoustoelasticity theory of rock is shown,which gives the theoretical relation between the ultrasonic wave velocity and in-situ stress of rock. Second,based on the acoustoelasticity theory of rock,an ultrasound method for determining the in-situ stress of rock is presented. The velocity variation of ultrasonic waves along a borehole surface before and after overcoring is measured,based on which the in-situ stress can be back analyzed. Last,numerical example shows the influence of rock stresses on wave velocities along the borehole surface. The numerical results reveal that this method can effectively determine the magnitude and the direction of in-situ rock stresses.