New aromatic polyformamidines were prepared by reaction of triethyl orthoformate with aromatic diamines containing various flexible linkages such as ether, isopropylidene, and hexafluoroisopropylidene between aromatic rings in N.N-dimethylsufoxide(DMSO) via high temperature solution polycondensation. The proposed structures of the resultant polymers were confirmed by elemental analysis, IR- and $^1$H-NMR spectroscopy. These polymers had inherent viscosities up to 0.42 dL/g, and most of them could be readily soluble in aprotic amide solvents including N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and DMSO at room temperature. Wide angle X-ray diffractograms(WAXD) revealed that the polymers were partially crystalline or amorphous. The glass transition temperatures of the polymers could be determined by differential scanning calorimetry (DSC) and were in the range of 118∼245 $^{circ}C$. Thermogravimetric analysis(TGA) indicated that the polymers are stable in nitrogen up to 300 $^{circ}C$, and 10％ weight loss occurred in the temperature range of 320∼395 $^{circ}C$ in air.