Over the past decades, realizing room-temperature superconductivity has become the tireless pursuit of scientists. Guided by the ‘chemical precompression’ theory, hydrogen-rich compounds have emerged as prime candidates for high-temperature superconductors, positioning them at the forefront of superconducting materials research. Extensive computational studies have identified numerous binary hydrides with predicted superconducting transition temperatures (T_c) exceeding 200 K, such as CaH₆, H₃S, MgH₆, YH₆, YH₉, YH₁₀, and LaH₁₀ et al. Significantly, the high-T_c of H₃S, LaH₁₀, CaH₆, YH₆, YH₉ has been experimentally confirmed. Compared to binary hydrides, ternary hydrides offer more diverse chemical compositions and structures, potentially leading to enhanced properties. Zhang et al. theoretically designed a series of AXH₈-type (A = Sc, Ca, Y, Sr, La, Ba; X = Be, B, Al) ternary hydrides with “fluorite-type” backbone, which were predicted to exhibit high-T_c under moderate pressure. Among them, LaBeH₈ has been experimentally confirmed to achieve a T_c of 110 K at 80 GPa. The T_cs of ternary clathrate hydrides of Li₂MgH₁₆ and Li₂NaH₁₇ have been predicted to be significantly surpassing the room temperature, while the required stabilization pressures all exceed 200 GPa. Xie et al. and Liang et al. independently predicted CaYH₁₂ compounds with Pm-3m and Fd-3m space groups, both of which exhibit high-T_c above 200 K at about 200 GPa. Other ternary hydrides, such as La-B-H, K-B-H, La-Ce-H, and Y-Ce-H, have also been extensively investigated. At current stage, a major focus of superconducting hydrides is to achieve high-temperature superconductivity at lower pressures. In this study, taking Pm-3m (CaYH₁₂) as a representative, we systematically investigated the effects of electron and hole doping on the dynamical stability and superconductivity in ternary hydride by first-principal calculations. The Pm-3m (CaYH₁₂) exhibits a T_c of 218 K at 200 GPa, which is consistent with previous report. When decompressing to below 180 GPa, imaginary phonons emerge. The analysis of doping simulations demonstrated that the electron doping exacerbates the softening of the imaginary phonons, whereas hole doping eliminates the imaginary frequencies. At the pressures of 130 GPa, 100 GPa and 70 GPa, the Pm-3m (CaYH₁₂) phase can be stabilized by hole doping at the concentration of 0.9e/cell, 0.8 e/cell, and 1.1 e/cell, respectively. Further electron-phonon coupling calculations show that the T_cs of Pm-3m (CaYH₁₂) at 130 GPa, 100 GPa and 70 GPa are 194 K, 209 K, and 194 K at the corresponding doping level, which are only 10-20 K less than the T_c at 200 GPa. At the pressure of 70 GPa, T_c slightly decreases to 189 K at a doping level of 1.2 e/cell, primarily due to the reduced ω_log compared to the case of 1.1e/cell. And the enhanced λ at 1.2 e/cell is mainly contributed by the average electron-phonon coupling matrix element $\left\langle I^2\right\rangle$ and average phonon frequency $\left\langle\omega^2\right\rangle^{1 / 2}$, rather than the electronic density of states at the Fermi level N(ε_F). These results indicated that hole doping represents a promising and effective strategy for optimizing the superconductivity of Pm-3m (CaYH₁₂) by maintaining high-T_c at low pressures. Our study has paved an avenue for realizing high-temperature superconductors at low pressure.