Phosphorus-containing hyperbranched aromatic-aliphatic polyamides are prepared via direct polymerization of triacid (B 3 ) with different diamines (A 2 ), which for improving the processability of aromatic polyamides while keeping exellent thermal and mechanical property. The triacid (B 3 ), tris(2-carboxyethyl)phosphine oxide (TCEPO), is synthesized from tetrakis(hydroxymethyl)phosphonium sulfate and its structure is verified by Fourier transform infrared, 1 H, 13 C and 31 P NMR spectroscopy. Then, the polycondensation reaction of TCEPO with p-phenylene diamine, 4,4′-oxyphenylene diamine and 4,4′-methylenedianiline result in three phosphorus-containing hyperbranched aromatic-aliphatic polyamides, and the degree of branching is found between 0.66 and 0.71. Gel permeation chromatography measurement reveal that all hyperbranched aromatic-aliphatic polyamides have moderate number-averaged molecular weights and narrow molecular weight distribution. The Dynamic mechanical thermal analysis results show all polymers have two glass transition temperatures (T g ) in the temperature range 85.3-128.0°C and have high storage modulus about 1.52-3.19 GPa at 50°C. The TGA results reveal the initial degradation temperatures (T 5 ) and the temperatures for 10% gravimetric loss (T 10 ) for the hyperbranched aromatic-aliphatic polyamides are in the range of 214-250 and 256-333°C, and the maximum decomposition temperatures (T m ) are about 500°C, and also the char yields of polymers at 850°C are about 39.4-48.4%, which indicate good thermal stability.