Environmental control of historical sites in archaeological museums faces challenges of high-energy consumption and complex soil-air coupled preservation environment. Many historical sites are not well preserved and undergo deterioration because of the desiccation cracking and salt enrichment. Moreover, the desiccation cracking cannot be prevented even if the air relative humidity (RH) is sustained to near-saturated state. This is due to the reason that migration of moisture from the historical site to air environment is a spontaneous one-way process. In the current work, a protection strategy, dealing with the air supplied into a "super-saturation" state through indirect-direct evaporative cooling (IDEC) and ultrasonic atomizing humidification (UAH) units, was proposed to provide a stable preservation environment and suppress the relics' deterioration. An experimental system, which consists of a simulated exhibition hall as well as an IDEC unit, was built. A series of tests were conducted to investigate the feasibility and performances of the system under different operational modes. The results show that: 1) the IDEC system could stabilize a preservation environment at the temperature of 24.4 degrees C, and relative humidity (RH) of saturation state (RH = 100%). The short-term fluctuations of temperature and RH are +/- 1.7 degrees C and +/- 0.0%, respectively, which conforms to the level-AA (risk-free) standard specified in ASHRAE. Moreover, it could effectively recover water content of the dried soil environment for the historical sites. 2) The system could manipulate precise temperature when the auxiliary surface air cooler (SAC) unit is switched on. Compared with a traditional return air operational system, it saves 40% of the energy consumed. The proposed system is of high-efficiency and provides energy-saving for the environmental control of historical sites. (C) 2019 Elsevier Ltd. All rights reserved.