The invention relates to an electricity quantity monitoring system and method, in particular an electricity quantity monitoring system and method of electricity-theft-prevention power equipment. The system is used for the electricity quantity monitoring of equipment which operates repeatedly each day. The system includes the following components that: a data acquisition module used for acquiring the power load data of the equipment and corresponding time information in real time; a feature extraction module for processing the acquired power load data and extracting feature data; a database used for storing the set feature data of the equipment in each time period; an electricity quantity monitoring module used for comparing the extracted feature data with the feature data of the equipmentin the database in corresponding time to obtain the electricity use parameters and electricity use states of the equipment, wherein the electricity use states include a working state and a state indicating whether electricity use power is within a set threshold range; and an electricity use control module used for issuing control instructions to the equipment according to the electricity use parameters and the electricity use states so as to determine whether electricity theft occurs on the equipment.