Load redistribution attack has impact on both the real-time outage model of a transmission line and the optimal load reduction model of power systems. Existing studies ignore the impact of LR attack on the real-time outage model, and thus cannot accurately reflect real-time operational risk to the power system. To tackle this issue, the principle of LR attack is analyzed, and operational reliability models considering the dual effects of LR attack on line real-time outage and system optimal load reduction are established. Then a power system operational reliability evaluation algorithm considering the dual effects of LR attack is proposed. Case studies have been conducted on an IEEE14 modified test system. Results show that LR attack has a great impact on the scheduling behavior of system operators, and the load reduction caused by the non-optimal scheduling of operators under LR attack is related to the number of attack resources. LR attack may increase the real-time outage probability of some lines. This reduces the reliability of real-time system operation. The research can provide a reference for the planning design and dispatching operation of a cyber physical power system.