As rock materials suffered from high temperatures, their mechanical properties, and physical parameters will be changed greatly, thus temperature has a great influence on the stability of geological engineering. In this study, a cracked straight-through Brazilian disc (CSTBD) specimen was applied to investigate the fracture behavior of two types of rock materials (hard rock and soft rock) under high temperature, which was made of granite and green sandstone and heating temperature from 25 °C (room temperature) to 700 °C. The changes in the mineral component of the granite and green sandstone materials with the temperature were obtained. The electro-hydraulic servo press was used for uniaxial compression tests, scanning electron microscope (SEM) was also used to observe fracture morphology and fractal dimension was calculated after high-temperature treatment, the relationship between the macro and microdamage mechanism of high-temperature treatment on rock materials was built. The experimental results can conclude that: (1) High temperature has a great effect on the changes in rock mineral components. After thermal treatments, the biotite in the granite is reduced, and the nimite in the green sandstone is reduced. (2) It can be found that the static fracture toughness of granite falls far more than that of green sandstone. When the temperature is over 600 °C, granite deformation becomes an obvious plastic failure feature and when the temperature is over 500 °C, green sandstone deformation becomes an obvious plastic failure feature. (3) The fractal dimension of the fracture surfaces of the green sandstone and granite is inversely proportional to the static fracture toughness. The fractal dimension of the green sandstone is larger than that of the granite.