The steer-by-wire system is a key part of the development of autonomous driving technology, and its reliability directly affects driving safety. The randomness of intermittent faults and the complexity of imperfect maintenance pose significant challenges to the design of fault prediction methods. Therefore, how to solve the intermittent fault prognosis problem of the steer-by-wire under imperfect maintenance is of great significance for driving safety. This article innovatively proposes an intermittent fault prediction method for the steer-by-wire system in the presence of imperfect maintenance based on the variable-size window and the operation condition-dependent compound degradation models. Extracting two features of intermittent fault through the concept of variable size window, the operation condition-dependent compound degradation models incorporating the effect of imperfect maintenance are formulated to predict the remaining useful life of the intermittently faulty component. The experimental results show that the developed method can achieve the relative accuracies of remaining useful life prediction with 95. 48% and 96. 14% under two operation conditions, which is obviously superior to the methods used in the existing literatures for comparative experiments. Keywords: steer-by-wire system; intermittent fault; imperfect maintenance; variabl