The increased complexity of power system makes the power dispatch heavily rely on the condition monitoring and state estimation functions. However, with the massive deployment of cyber technologies, the power grid is becoming more vulnerable to malicious cyber attacks, including various kinds of false data injection attacks. This paper quantifies the influence of load redistribution (LR) attack on the long-term power supply reliability. The intrusion process for manipulating the measurements is modeled by the semi-Markov models. Considering the practical cross-check for suspicious measurements, the regional LR attack model is proposed. A holistic framework incorporating the physical failures and the LR attack is proposed for cyber-physical power system reliability evaluation. The simulation is carried out on the IEEE RTS79 system. The influences of critical factors and strategies are analyzed. It is concluded that the LR attacks have a non-negligible impact on the power system reliability.