A series of polyacrylonitrile/polyimide (PAN/PI) composite films with different PAN contents are prepared under given curing temperatures (250, 300, 350, and 400°C). The microstructure of the composite films is observed by SEM, and the thermal, dielectric and mechanical properties of the composite films are determined. The results show that the self-assembly behavior of polyamic acid gives rise to connected network structure in the composite films and the variations in the microstructure of the composite films cured at different temperatures show important effects on the properties of PAN/PI composite films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40283.