Under low temperature and hot pressure molding process, the unidirectional C/C composites is prepared with PAN-based carbon fiber and AR-mesophase pitch. The effects of The heating program, heating time, the carbon fiber content, the temperature of pressure starting and pressure value on prepared sample are investigated. The morphology of C/C composites preform were characterized by polarizing optical microscope (POM). The results show that the optimization conditions are as follows: 60% of the carbon fiber content, 9h from 350°C to 550°C of heating time and the pressure of 44MPa at 450°C. The density of C/C composites compact preform is up to 1.43g ·cm-3 under the optimization condition.