The surface of polysulfonamide (PSA) fiber was modified by air plasma to improve its wettability and interfacial bonding performance. The surface morphology and chemical composition of the fiber were then evaluated with fieldemission scanning electron microscopy (FESEM) and X-ray photoelectron spectrometry (XPS). Moreover, the wettability and interfacial bonding performance of fiber before and after air plasma treatment were examined by water absorption time and interfacial shear strength (IFSS). FESEM observation confirmed that PSA fiber surface roughened with prolonged treatment duration. XPS analysis showed that the O/C atomic ratio on the PSA fiber surface can be increased from 19.69 % to 38.59 % after 3 min of treatment. Water absorption time dropped from as much as 400 s to about 0 s, indicating that the wettability of the fiber greatly improved. Under the experimental conditions of 40 Pa pressure, 100 W power, and 3 min treatment duration, IFSS increased by 57.01 %, and the interfacial bonding performance of fiber greatly improved.