The invention provides an electric energy quality transient event monitoring method and device. The electric energy quality transient event monitoring method includes the steps that electric signal sampling data of monitored alternating currents in the current monitoring period is obtained and buffered; electric signal sampling data of monitored alternating currents obtained within the set periodbefore the starting moment of the current monitoring period and buffered in advance is read; the set period is the difference between one second of the electric signal period of the monitored alternating currents and the current monitoring period; the semi-wave effective value of the monitored alternating currents is determined according to the electric signal sampling data of monitored alternating currents in the current monitoring period and the electric signal sampling data of monitored alternating currents obtained within the set period before the starting moment of the current monitoringperiod and buffered in advance; if the semi-wave effective value is larger than a set threshold value, it is judged that an electric energy quality transient event occurs on the monitored alternatingcurrents. Based on this, transient event monitoring is prevented from missing, and the accuracy of monitoring the electric energy quality transient event is improved.