In this study, the unconfined compression experiments of the intervertebral disc were conducted by applying an optimized digital image correlation (DIC) technique, and the internal strain distribution was analyzed for the disc. It was found that the anulus fibrosus (AF) radial displacement was outward in all the six test regions: inner AF, middle AF and outer AF both in anterior and posterior region. Middle AF exhibited the highest radial strains both in posterior AF and anterior AF with the increase of loads. It was noted that all samples demonstrated a nonlinear axial stress-axial strain profile in the process of deforming, and demonstrated an elastic region once the sample was deformed beyond its toe region. Inner AF exhibited the highest axial strains, while outer AF exhibited the lowest axial strains during static compressive loading. This study provides important new data in understanding the internal strain distribution, and provides a technique and baseline data for evaluating surgical treatments.