A model of failure detection behavior of human operator who is actively controlling a linear system or passively monitoring a display is proposed in this paper. Estimation and signal detection theory are applied to the development of the model. In this model, the failure detection mechanism is expressed by likelihood ratio function based on Wald's Sequential Probability Ratio Test; prediction of signals, visual cue and stick travel, recognized by operator is described by two autoregressive model each correspond to hypothesis H0 (system is normal) and to H1 (system is failed). The remarkable feature of this model is that proprioceptive infomlation generated by control manipulation is included in the model as available information for controller addition to visual display information. Detection time and detection accuracy predicted by the model are in good agreement with the experimental data over a wide range investigated for both case of controller and monitor.