<p>The measurement of envelope deformation is a crucial component of structural health monitoring for stratospheric airships. This paper offers an improved approach for monitoring the deformation of airship envelopes based on digital image correlation, highlighting the advantages of non-contact operation and full-field visualization. Due to the complex operational scenarios of stratospheric airships and the high computational cost of traditional image interpolation-based iterative methods, it is challenging to achieve skin sub-pixel displacement measurement efficiently. To this end, building on algorithmic innovation and experimental design, we propose a novel sub-pixel displacement searching strategy that combines the Gaussian peak approximation with finite-difference calculation and further validate the strategy through a dedicated experimental protocol implemented on a ground-based airship. Experimental results demonstrate that the proposed method enhances measurement accuracy while maintaining computational efficiency and captures the complex non-uniform deformation patterns of the airship envelope during pressurized inflation. In short, our method provides reliable data for stratospheric airship skin deformation analysis and offers a solid technical solution for airship structural health monitoring.</p>