The deep integration of power grid and information network enhances the controllability of the power system while reducing its ability to resist external interference. Firstly, an interdependent model of cascading failures in the cyber-physical power system (CPPS) was established based on the proposed load redistribution scheme using node load and capacity probabilities. This model was used to investigate the robustness and controllability changes in the CPPS under different coupling strategies. Secondly, the concept of surviving load percentage was utilized to quantify the power grid's ability to withstand cascading failures. The effects of different coupling strategies and capacity parameters on the robustness and controllability of CPPS were analyzed. The assessment method for power node importance was proposed based on network controllability theory and validated in the IEEE39 system. The research results indicate that the coupling of high-betweenness nodes in the power grid and high-betweenness nodes in the information network leads to a stronger resistance to interference in the power information physical network, and the capacity parameters of power grid nodes have a greater impact on the system compared to the capacity parameters of information network nodes.