Background <p>It is of great significance to study the internal and surface crack extension of rock. Currently, there are few studies on quantitative observation of internal deformation of rocks, and there is a lack of correlation analysis between internal and external deformation.</p> Objective <p>The objective of this study is to develop a test method capable of testing the internal deformation and stress deflection towards the rock, and to investigate the relationship between the model surface cracking and the internal stress change, the evolution law of the rupture mechanism during the model cracking process, and the influencing effect played by the compressive strength.</p> Methods <p>The techniques employed in this study include the embedded strain-cubes technique, digital image correlation system and acoustic emission technique, and rock-like models.</p> Results <p>Select the upper end of the prefabricated fissure for analysis, during the yield stage, the maximum local principal strain in the model increases significantly, and the growth is more obvious in the dilatation quadrants, the number of small-scale tensile cracks in the model increases, and the local deformation parameters within the model are strongly correlated with both the overall model strain and the cumulative acoustic emission energy.</p> Conclusions <p>As the strength decreases, the model is less prone to local deformation before the yield stage, the model plastic deformation is obvious, the fluctuation of the deflection angle is gradually distributed from the yield stage to the compaction stage, and the rupture mode transitions from being predominantly shear-dominated damage to a mixed tensile-shear failure mechanism.</p>