New aromatic polyimides (PIM and PIP series) having silicone moieties in the main chain were prepared by the polycondensation reaction of meta- and para-oriented silphenylene/siloxane containing monomers with spiroacetal and other aromatic monomers. The monomers employed were 1,3-bis(m-aminophenyl)-1,1,3,3-tetramethyldisiloxane(DMDA) and 1,3-bis-(p-isocyanatophenyl)-1,1,3,3-tetra-methyldisiloxane (DMIS). The structures and thermal properties of these polymers were determined by FT-IR, 1^H-NMR, elemental analysis, WAXD, DSC, and TGA. PIM and PIP series of polymers had inherent viscosities in he range of 0.25-0.41 dL/g. They were readily soluble in various organic polar solvents such DMF, DMAc, and NMP. The T_g and T_m of these Polymers were detected over the temperature range of 100-170℃ and 245-315℃, respectively, according to their DSC traces. The thermal stabilitles of these polymers were also evaluated by TGA, which showed that their IDT and T₁₀ were in the range of 290-400℃ and 312-415℃, respectively, under the nitrogen atmosphere. WAXD patterns of PIM and PIP series showed that their structures were semi crystalline.