To investigate the effects of polypropylene fiber ( PPF) content and prefabricated crack angle on the crack propagation and failure mode of concrete under compression, uniaxial compression tests were conducted on plain concrete and polypropylene fiber concrete (PFRC) with different crack angles. The internal damage process was collected using an acoustic emission (AE) monitoring system, and the failure mode and AE localization map of specimens were analyzed. The relationship between PPF content, prefabricated crack angle, stress-strain curve, AE parameters and other indicators was explored. Research has shown that as the content of PPF increases, the number and propagation range of cracks in specimen decrease first and then increase, and the peak stress increases first and then decreases. Its failure mode changes from tensile failure to tensile shear or shear failure. The mechanism of PPF is that when the content is appropriate, it can play a good bridging role inside the matrix, while when it is excessive, it is easy to form clusters, leading to an increase in internal weak surfaces, indicating that PPF has positive and negative effects on the reinforcement effect of concrete. As the angle of prefabricated cracks increases, the peak stress shows a trend of decreasing first and then increasing. Among them, there is a certain synergistic effect between inclined non horizontal angle prefabricated cracks and high content PPF, and several types of prefabricated crack angles that are sensitive to changes in compressive strength and PPF content of the specimens are found. Finally, analyzing the AE data, it is found that the addition of PPF increases the number and distribution of positioning points in the AE localization map. The activity time of AE signals from the beginning to the peak is prolonged with the increase of PPF content, indicating that PPF has a crack resistance and toughening effect on concrete.