The invention discloses a multitime voltage sag severity evaluation method. The method comprises the following steps: detecting voltage sag amplitude and continuous time of voltage sag each time; based on a preset sensitivity index of voltage sag, integrating the voltage sag amplitude and the continuous time, and constructing a voltage sag severity index based on this; and substituting the voltage sag amplitude and the continuous time into the voltage sag severity index, and calculating voltage sag severity of multiple times. According to the multitime voltage sag severity evaluation method disclosed by the invention, the sensitivity of the voltage sag amplitude and the continuous time of the voltage sag each time is taken into consideration, the sensitivity of major factors influencing severity evaluation are integrated, the severity evaluation index of the voltage sag each time is formed, and thus severity evaluation of the voltage sag of multiple times in short time can be realized. The invention further discloses a multitime voltage sag severity evaluation system. The system has the aforementioned advantages.