Abstract: A centralized remote-supervisory system and a data acquisition method therefor, wherein the system includes a central processing unit and a plurality of terminal units connected to the central processing unit, each terminal unit including sensors. The central processing unit of the system provides a criterion value corresponding to each of a plurality of time zones, and transmitting the criterion value to the terminal unit, wherein the criterion value is utilized for forming a threshold level used in the terminal unit. The terminal unit of the system compares a differential between a current detected data and a previously detected and stored data with the threshold level, and selectively transmits the current detected data to the central processing unit and replaces the previously detected and stored data with the current detected data when the differential is larger than the threshold level.