Cognitive disturbance in identifying, processing, and responding to salient or novel stimuli are typical attributes of schizophrenia (SCH), and P300 has been proven to serve as a reliable psychosis endophenotype. The instability of neural processing across trials, i.e., trial-to-trial variability (TTV), is getting increasing attention in uncovering how the SCH “noisy” brain organizes during cognition processes. Nevertheless, the TTV in the brain network remains unrevealed, notably how it varies in diferent task stages. In this study, resorting to the time-varying directed electroencephalogram (EEG) network, we investigated the time-resolved TTV of the functional organizations subserving the evoking of P300. Results revealed anomalous TTV in time-varying networks across the delta, theta, alpha, beta1, and beta2 bands of SCH. The TTV of cross-band timevarying network properties can efciently recognize SCH (accuracy: 83.39%, sensitivity: 89.22%, and specifcity: 74.55%) and evaluate the psychiatric symptoms (i.e., Hamilton’s depression scale-24, r=0.430, p=0.022, RMSE=4.891; Hamilton’s anxiety scale-14, r=0.377, p=0.048, RMSE=4.575). Our study brings new insights into probing the time-resolved functional organization of the brain, and TTV in time-varying networks may provide a powerful tool for mining the substrates accounting for SCH and diagnostic evaluation of SCH.