Aiming at the deficiencies existing in the DC/DC circuit fault prediction with distance as the fault characteristic parameter, the Piecewise Dynamic Time Warping (P_DTW)distance is proposed as the fault characteristic parameter of DC/DC circuit, which is used together with the Long Short-Term Memory (LSTM) algorithm for the fault prediction of DC/DC circuits. First, the circuit output voltage is chosen as the monitoring signal. Then, the dynamic time warping algorithm is used to calculate its P_DTW distance with the faultless output voltage, which is used as the fault characteristic parameter of the circuit. Finally, the time series prediction of circuit fault characteristic parameters is implemented based on the LSTM prediction model.The Boost circuit is taken as an example to verify the effectiveness and accuracy of the proposed method.