To aid the development of air filters with high-efficiency fine particulate matter (PM) capture properties, the electrospinnabilities of natural cellulose nanofibers, which considerably affect filter performance, were investigated via rheological behavior analysis. The cellulose nanofibers were prepared by mixing trifluoroacetic acid (to dissolve cellulose) and 1,2-dichloroethane (to improve electrospinnability) with various types of cellulose. The rheological behavior of the precursor solution was analyzed according to mixing time via large amplitude oscillatory shear studies. The electrospinnability of the cellulose precursor solution was investigated based on the flow-induced structural anisotropy characteristics and the storage-loss moduli plot obtained by varying the frequencies. The precursor solution with hardwood pulp (HP) exhibited the highest specific surface area and the lowest combined content of hemicellulose and lignin, and thus, the optimal electrospinnability. The electrospun HP nanofiber sample with an HP content of 1.5 wt% displayed the optimal electrospinnability and the highest specific surface area of 1021 m²/g. It also exhibited high-efficiency PM capture characteristics, such as a PM_2.5 capture efficiency and quality factor and an air permeability of 98.99%, 0.27, and 309 cm³/cm² s, respectively. This study suggests the potential for the development of next-generation green nanofiber air filters using cellulose nanofibers.