Small-angle X-ray scattering patterns of polyaniline (PANI) complexes/polyimide (PI) blends were observed in order to analyze the compatibility between two components of the blends. From the experimental results, it was concluded that the microphase separation or molecular level mixing, which was the reflection of compatibility, was dependent on the kinds of dopant (camphorsulfonic acid (CSA) and dodecylbenzene sulfonic acid (DBSA)), PANI content and the imidization state. On account of self-assembling nature of PANI-DBSA, PANI-DBSA/poly(amic acid) (PAA) shows phase-separated morphology. On the other hand, PANI-CSA/PAA blends exhibited well mixed and high compatible morphology. Thermal curing of these blends brought about the change of blend morphology, which was in correlation with altered chain structure from PAA into PI, and was also a function of PANI content. It was supposed that conversion from PAA to PI by thermal curing processes led to enhancement of compatibility probably due to higher interaction between two components.