In view of the fact that rocket-assisted zero-length launch (ZLL), as the mainstream takeoff method for high-speed UAVs, relies on the dynamic stability of its multi-rigid-body connected structure, which is critical to the success of the launch, a field emergency assessment method based on digital image correlation (DIC) technology has thus been proposed to address the rocket-body connection pose deviation brought about by abnormal engine vibrations. By constructing a simplified optical measurement system adapted for the field environment, a real-time capture, as well as an analysis of the displacement field of the rocket booster system, can be achieved. To address the lack of speckle patterns under non-laboratory conditions, natural textures on the surface of UAV composite materials and processing marks on the rocket body are utilized as alternative speckle sources, combined with grayscale adaptive algorithms so as to improve matching accuracy. Test results show that when the engine speed rises to 96,000 revolutions per minute (r/min), the horizontal displacement difference between the rocket body is 0.3 pixels (corresponding to a physical displacement of 0.12 mm), and the vertical displacement difference is 0.5 pixels (0.20 mm), which is far below the safety threshold (±2mm). In subsequent multiple field launch verifications, the standard deviation of the system pose offset remains within 0.15 mm, with the launch success rate reaching 100%.