Xylok polybenzoxazine with acetylene group terminals (XPBZAs) were synthesized by the Mannich-like condensation of Xylok prepolymer, formaldehyde, aminophenylacetylene, and aniline, and their structures were characterized by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR). The curing behavior of XPBZAs was determined by differential scanning calorimetry and FTIR. Thermal behavior and dynamic mechanical properties of the cured XPBZAs were investigated using thermogravimetric analysis and dynamic mechanical analysis. The results showed glass transition temperature (Tg), the thermal stability, and anaerobic char residue of cured XPBZAs increased as the content of acetylene groups increased. POLYM. ENG. SCI., 50:1751–1757, 2010. © 2010 Society of Plastics Engineers