In this article, the isothermal decomposition dynamics research instrument was used to investigate the interaction between three hydrogen absorbents and AlH3, including C60, C70, and 1,4-bis (phenylethynyl) benzene (DEB). The gas volumes emitted by AlH3, AlH3/C60, AlH3/C70, and AlH3/DEB during the 48 h vacuum stability experiment were 2.85, 2.41, 1.92 and 2.02 mL/g, respectively. The isothermal thermal breakdown of the three materials was investigated simultaneously at 333–393 K. The isothermal thermal decomposition kinetic parameters of AlH3/C60, AlH3/C70, and AlH3/DEB were determined using the Arrhenius and model-fitting method by using the pressure–time curve of the decomposition and release gas of the mixed sample of AlH3 and three hydrogen absorbents. AlH3/C60, AlH3/C70, and AlH3/DEB had activation energies of 118.2, 116.9, and 116.8 kJ·mol−1, respectively and pre-exponential factors of 20.49, 20.16, and 20.19, respectively. By using XRD and TEM, the thermal breakdown products were examined.