Abstract Recently, many encouraging experimental processes have been achieved in ternary hydrides superconductors under high pressure. However, the extreme pressure required is indeed a challenge for practical application, which promotes a further exploration for high temperature (T c) superconductors at relatively low pressure. Herein, we performed a systematic theoretical investigation on a serious of ternary hydrides with stoichiometry AX$_2$H$_8$, which is constructed by interacting molecular XH$_4$ (B, C, and N) into the fcc metal A lattice under low-pressure range of 0-150 GPa. We uncovered five compounds which are dynamically stable below 100 GPa, e.g., AcB$_2$H$_8$ (25 GPa), LaB$_2$H$_8$ (40 GPa), RbC$_2$H$_8$ (40 GPa), CsC$_2$H$_8$ (60 GPa), and SrC$_2$H$_8$ (65 GPa). Among these, AcB$_2$H$_8$, which is energetically stable above 2.5 GPa, exhibits the highest T c value of 32 K at 25 GPa. The superconductivity originates mainly from the coupling between the electron of Ac atoms and the associated low-frequency phonons, distinct from the previous typical hydrides with H-derived superconductivity. Our results shed light on the future exploration of superconductivity among ternary compounds at low pressure.