In this paper, a practical cascading model used for investigating the impact of virus propagation on the cascading failure of cyber-coupled power system is proposed. The model takes into account the actual functionality of coupled system and dynamic virus propagation in cyber network, and describes the effects of cyber node failure caused by virus infection and power flow overload on the cascading failure propagation. Centralized control based on dispatching center and local regulation based on power-frequency characteristic are introduced to describe the actual monitoring function of cyber system on power grid. Then, the effects of physical immunity and modular community structure on failure evolution are analyzed. The results indicate that the spread of virus destroys the monitoring function of cyber network on power grid and leads to more serious failure results. Moreover, global target immunity and local community bridge immunity can effectively mitigate the impact of virus infection on the cyber-coupled system. In addition, the stronger the community structure of cyber network, the more conducive to improve the robustness of cyber-coupled power system.