Environmental fatigue crack propagation of CF8M and CF8A steels used in the domestic nuclear power plants (NPPs) were investigated on the simulated pressurized water reactor (PWR) condition (temperature: 316°C, pressure: 15MPa). The test equipment for environmental fatigue (high temperature-high pressure loop, autoclave, load frame, and measurement system) was designed. As-received and 60-year aged specimens were used in the test. To compare with environmental fatigue test, another test in the air condition was performed. The fracture surfaces of specimens were difficult to verify the fracture modes such as striation, inter-granular crack and cleavage and so on. As the ferrite content of CF8M is increased, more particles on the fracture surface were peeled.