The present study attempts to establish a correlation between the macromolecular parameters obtained from small angle X-ray scattering (SAXS) analysis of pretreated sunn hemp (Crotalaria juncea) fibers with the dielectric and mechanical properties of their composites. Sunn hemp fiber is pretreated chemically by dewaxing and alkalization methods and physically by microwave irradiation. The treatment effect is structurally investigated using a correlation function from SAXS data and correlated with the mechanical as well as electrical properties of composites. The macromolecular parameters are observed to be influenced by pretreatment methods. Macromolecular structural modifications are seen in dewaxed fiber (DSHC), fiber treated with 10% of alkali soaked for 6 h (10K6C), and fiber microwave irradiated with 800 watts for 6 min (800W6M), improving the mechanical as well as electric properties of the reinforced composites.