One of the most important goals of the experiments is to determine deformation and strength of the rock specimen under applying triaxial load, the status of failure condition is one of the subjects which can be used in soil mechanic and foundation engineering applications. To investigate the effect of confining pressure on the triaxial test, the rock has been considered as bonded-particles method and has been simulated by particle flow code three dimensions (PFC3D). This model, does not have pre-existing microcracks and all the particles have the same size (2 mm diameter), equal to the real specimen shape. To compare the mechanical behavior and failure pattern of the numerical and experimental results at uniaxial and triaxial tests at the same conditions, the Young's modulus, Possion's ratio as well as maximum axial stress have been considered. On the other hand, the microcracks growth and change of failure pattern at the modelling of the uniaxial and triaxial tests with different confining pressures up to failure point were reported. According to the experimental work, the number density of microcracks decreases from starting value and remains almost constant up to the failure beyond that point. The comparison of the numerical and experimental results of maximum axial stress and the Possion's ratio revealed good accordance. The initial number density of microcracks at the model was zero and increased while microcracking. Also, the sudden increment around the maximum stress was observed which is because of unstable growing of microcracks near the maximum stress. In all uniaxial and triaxial tests with different confining stresses, the number density of microcracks during the failure remains almost constant which can be considered as a proof of failure occurring in the model. The experimental results indicate the similar trend as well.