Abstract: With the acceleration of urban renewal, the renovation of old libraries faces dual challenges of limited power expansion and strict book collection protection. This study proposes a lightweight transformation model based on intelligent operation and maintenance. Taking two typical cultural heritage libraries in Shanghai as research objects, a closed-loop system of "perception-decision-execution" is constructed through the integration of BIM IoT rule engine technology. In terms of power regulation, innovative equipment group control strategies and time-sharing load models are used to achieve flexible release of power capacity; In the field of environmental control, establishing high-density sensor networks and adaptive control models significantly improves the accuracy of temperature and humidity control; Simultaneously integrate structural health monitoring and biological intelligent prevention and control systems, and improve the full cycle operation and maintenance of cultural security facilities. Practice has shown that this method effectively alleviates equipment operation conflicts and literature degradation risks without breaking through existing power capacity, forming a replicable low-cost transformation path. The research results provide a technological integration innovation paradigm for the functional renewal of historical buildings, and its core logic of "algorithm replacing hardware" has important reference value for the renovation of similar old buildings.