In this paper, 7055-TO Al alloy is taken as the research object and the two processes of ultrasonic vibration and creep aging forming are combined. The numerical simulation method is used to investigate the influence of vibration parameters and stress superposition effect on the mechanical properties and deformation behavior of the creep aging tensile (CAT) process for the specimen, and the forming force effect of the ultrasonic-assisted creep aging tensile (UVCAT) specimen and the CAT specimen are analyzed. It is found that the 7055-TO alloys are treated by UVCAT, the input of too high or too low ultrasonic vibration energy will lead to the increase of metal flow stress limit. When the frequency w of 20 kHz and the amplitude u of 12 mm are determined, the ultimate stress and average stress of the UVCAT specimen are reduced by 7% and 26%, respectively. The corresponding effective softening amplitude reaches the maximum of 26.5 MPa. It indicates that the stress superposition effect of the specimen treated by UVCAT is the most significant and its creep age tensile forming effect is the best.