Actuator rate limiting has been a causal or contributing factor for Pilot Induced Oscillations (PIO) experienced on highly augmented aircraft. The closed-loop pilot-aircraft system was the research object. The mechanism of PIO was examined. The pilot model and aircraft model about closed-loop system were set up. The effect of actuator rate limiting was discussed, The prediction methods of category Ⅱ PIO due to actuator rate limiting, OLOP criterion, were studied. A critical examination of the Open-Loop Onset Point (OLOP) criterion was conducted to see if it could accurately predict PIO due to actuator rate limiting and to evaluate its potential as a design tool.