Abstract: Recent advances in near room-temperature superconductivity, especially achieved in hydrogen-based superconductors under high pressure, have attracted broad interest. However, most systems with high superconducting critical temperature (Tc) can only stabilize under extreme pressures, which limits their practical applicability. Herein, this study proposes investigating the possibility of obtaining high-Tc superconductors at moderate pressures within the ternary Th–Y–H system. The synthesis was carried out using Th, YH3 and NH3BH3 as precursors under high pressure and high temperature, applied by diamond anvil cells combined with in-situ laser heating technology. Combining with the synchrotron XRD measurements and theoretical studies, the main product was identified as Fm-3m (Th,Y)H10, with Y accounting for approximately 10%~15%. Electrical transport measurements reveal that its Tc increases by approximately 10%, compared to ThH10 under similar pressure. At 144 GPa, the sample has a maximum Tc of 184 K, which remains at 170 K when decompressed to 100 GPa—approaching the highest level known for hydrides at this pressure. Measurements under an applied magnetic field further verify the superconductivity, with upper critical fields estimated at 52 T and 39 T based on the WHH and GL models, respectively. These results indicate that the ternary Th–Y–H superconducting system is an outstanding candidate for high-Tc superconductors, and the crystal stability and electronic properties can be effectively controlled by reasonably introducing new element into the binary system. This work provides new insights and experimental evidences for exploring high-Tc superconducting hydrides under moderate or even low pressures.