This research aims to implement an activities of daily living (ADL) monitoring system for elderly who lives alone. The active radio frequency identification (Active RFID) technology is employed to recognize the identity and activity area of the elderly. A health wristband wore on the elderly can extract activity parameters such as walking steps and energy expenditure. The obtained activity parameters are then sent to the remote server built in the monitoring center to construct activity density map (ADM) to watch if abnormal status happens via dissimilarity analysis. Experimental results verify the practical potential of the proposed monitoring system.