Recently, as periods of high concentration of fine dust have become frequent, the need for filters that can be applied not only indoors but also outdoors has been highlighted. Research on filters suitable for outdoor environments is relatively lacking, and since indoor filters are used the same way, supplementation is needed. In this study, a double filtration structure for outdoor air purification was designed and filter performance according to various filter combinations was analyzed. The filter performance evaluation was performed based on the ‘KS B 6141 Ventilation Air Filter Device’, and Arizona Test Dust A1 was used as the dust for filter evaluation. The double filtration structure is a two-stage capture structure in which a metal filter is placed in the front and a HEPA filter is placed in the back, and the particle capture efficiency and pressure drop were analyzed according to the Fiber Diameter of the metal filter, the grade of the HEPA filter, and whether it was pleated or not. Except for the structure combining a metal filter with a fiber diameter of 75 μm and an H11 grade HEPA filter in a flat plate shape in a dual filtration structure, a high particle capture efficiency of over 99% was observed in all types. The metal filter in the front of the dual filtration structure blocked coarse particles, and the gap between the two filters smoothly distributed air, showing a pressure increase of less than 8.5%.The proposed double filtration structure can replace expensive high-performance filters, resulting in cost savings, and it is also considered to be excellent from an environmental perspective because the metal filter can be washed and reused.