Abstract:The extensively used formula for estimating the tensile strength of rocks under the Brazilian test is based on the 2D elastic theory and only suitable for very long or very short cylinders. However,the size of specimen in practice does not meet these preconditions. Under 3D conditions,it is found out that height- to-diameter ratio and Poisson¢s ratio are two factors influencing the stress distributions in rock cylinders. Through 40 3D FEM simulations,the influences of the height-to-diameter ratio and Poisson¢s ratio upon the stress distribution within the specimen were studied. It is found that the largest tensile stress within the specimen is always at the center of end surface. A fitting formula of largest tensile stress is presented. Lastly,the largest equivalent stresses bases on Griffith strength theory and Mohr strength theory were calculated. And it is found the largest equivalent stress is not at the center of the end surface of cylinder but always at the loading point of the end surface. Therefore,the Brazilian test is not suitable to measure the tensile strength of rock-like materials.