Subwavelength thin-film stack metamaterials, as a special group of metamaterials, have attracted much attention owing to their subwavelength thickness, ease of fabrication, low-cost and large-area fabrication capacities, etc. In this article, the recent research progress of the theory and applications based on subwavelength thin-film stack metamaterials is reviewed. We first focus on the overview of the theoretical background and the newly developed techniques for subwavelength thin-film stack metamaterials. Then, we highlight the progress of recent applications, including structural colors, photoluminescence (PL) enhancement, thermal emitter and infrared stealth, etc. Finally, the future opportunities and challenges about further research on the subwavelength thin-film stack metamaterials are also addressed.