The utility model relates to a heat isolating and temperature lowering aggregate unit for effectively protecting the stability of the permafrost under the lower part of the civil engineering structure and used in the civil engineering structure on permafrost area. The structure of the utility model is that an air chimney is perpendicular to the foundation trend and is buried in a certain deep position of the earth bank. An automatic temperature control ventilating device is arranged on one end of the air chimney and heat-insulating materials are arranged between the air foundation and the air chimney or up the whole air chimney. Via the automatic control of the temperature control system for the inner earth body of the foundation, the inner earth body of the foundation exchanges heat only with the exterior low-temperature airflow. The heat-insulating materials arranged between the air chimneys or up the air chimney can interclude the external heat intrusion and hold the lower cold energy. Thereby, the heat budget balance of the permafrost is sustained, the stability of the permafrost is ensured and the engineering stability influenced by the frost heave and the thaw collapse in the cycle of freezing and thawing in the season active layer is effectively avoided. Making use of the combination of the natural cold energy clew, the new mechanical control measure has the advantages of outstanding potency, obvious temperature lowering effect, feasible engineering construction, relatively cheap manufacturing cost and wide application environment etc.