In order to investigate the influence of miscrowave excitation on the mechanical properties and cracking effect of hard limestone, the typical limestone in Xuzhou area was selected for microwave treatment and uniaxial compression experiment, and a two-phase rock model was established to carry out numerical experiments, and the law of the change of damage degree of limestone with microwave excitation power and time was analyzed. The results show: The changes in mechanical properties of limestone induced by microwave excitation included small cracks caused by temperature stress at the interface between two components. In addition, the temperature gradient and stress gradient at the interface of the two components are negatively correlated with the treatment time when the microwave power is constant. The optimum microwave excitation power and time of rock compression breaking are 3.0 kW/m³ microwave treatment for 10 min. With the increase of the distance from the central axis of the load point, the fracture stress curve under each excitation power shrinks continuously. As a key power node of microwave-stimulated rock fracture growth, 3.0 kW/m³ has significant influence on fracture growth gradient in different regions of rock samples. The results can provide reference for the cracking of hard limestone.