Waterborne polyamic acid (PAA) with twisted non-coplanar structure was designed and modified carbon fiber (m-CF) surface to establish high temperature resistance interface, and the correlations of heat-resistant interphase with interfacial and thermo-oxidative aging properties of CF/bismaleimide composites were investigated. Compared to pristine CF (p-CF) and commercial CF (c-CF), PAA sizing was still adhered on m-CF surface at 280 °C aging. Thermal degradation activation energy (Ea) of PAA/bismaleimide simulated interphase by Madhusudanan model was higher than that of c-CF/bismaleimide interphase after 10 days aging, resulting in enhanced transverse fiber bundle test strength and interlaminar shear strength retention and increased Ea of m-CF composites. Before and after aging, interphase modulus and thickness in m-CF composites was hardly varied, and interphase height line profiles in atomic force microscope topographies was transferred from “U” to “V” shape, which was attributed to improved high temperature interface from chemical bonding between PAA and bismaleimide and suppressive oxidative degradation of heat-resistant PAA/bismaleimide interphase.