With the continuous development of energy-saving doors and windows, energy-saving glass has gradually developed from a single-cavity insulating glass to a multi-cavity insulating glass. In order to improve the thermal insulation properties of doors and windows and reduce the weight of insulating glass system. A new double suspension film insulating glass system with three cavities composed of two pieces of glass, two layers of film was designed, which based on the structure of four-glasses three-cavities insulating glass. Using polyethylene terephthalate (PET) film as a diaphragm to replace the heavier glass in the middle of the four-glasses three-cavities structure. The key performance of the glass system was analyzed. Firstly, the expressions of stress and strain were derived. Secondly, the film stretching process was analyzed based on ABAQUS. Then, the advantages of the new double-suspension film insulating glass system were compared from the aspects of the whole window quality, thermal performance and cost. Finally, the design was proved to be feasible by variable temperature environment experiment. The analysis results show that compared with the four-glass three-cavity insulating glass system, the overall quality of the double-suspended insulating glass system is 47.5% lower, the cost is reduced by 87.5%, and the heat transfer coefficient is slightly higher by 6.67%, but the heat transfer coefficient is lower than that of the single-cavity insulating glass system. It is 63.7%, which effectively solves the problem of heavy weight of multi-glass insulating glass, and has better thermal insulation performance than single-cavity insulating glass and lower cost. This innovative structure is more advantages in engineering applications. [ABSTRACT FROM AUTHOR]