In order to study the law of crack propagation in roller compacted concrete layer shear process, this paper carried out shear strength tests on roller compacted concrete treated at different layers, and analyzed the failure modes and shear strength change law of different specimens. At the same time, digital image correlation technology was used to observe the development law of layer cracks in roller compacted concrete shear process, and the influence of hydration degree of layers on crack propagation was analyzed by thermogravimetric technology. The results show that the layer treatment can effectively improve the bonding effect and shear strength of layer, and reduce the crack width and propagation rate. The roller compacted concrete layer treated with nano-SiO₂ mortar has the best bonding effect, and the maximum crack width and propagation rate are reduced to 0.528 mm and 1.412 mm/s, respectively. The development process of layer cracks is divided into four stages: initial, initiation, expansion and connection. Nano-SiO₂ can promote the hydration of cement, and the content of hydration products is negatively correlated with maximum crack propagation rate. Therefore, the addition of nano-SiO₂ can effectively reduce layer crack propagation rate.