<p>Memristors based on metal oxides show great potential for neuromorphic computing. However, their practical implementation is often limited by high forming voltages and unstable switching behavior. In this work, Ca²⁺-doped Cu_xO memristors with an ITO/CuₓO(Ca)/ITO structure are fabricated via a solution-based spin-coating process, followed by thermal annealing and magnetron sputtering for top electrode deposition. The introduction of Ca²⁺ effectively eliminates the forming process, enabling stable forming-free bipolar resistive switching. A systematic investigation of devices with different Ca²⁺ doping concentrations (0%, 0.25%, 0.5%, and 0.75%) reveals that the optimal performance is achieved at 0.5% doping. The optimized device exhibits a high ON/OFF ratio (&gt; 10), stable set/reset voltages, an endurance of over 10⁴ cycles, and a retention time exceeding 10⁴&#xa0;s. This improvement arises from Ca²⁺-induced defect engineering in Cu_xO films. The increase in Cu⁺ content and the reduction in film thickness exert a synergistic effect, thereby promoting the stable formation and rupture of conductive filaments. Furthermore, the optimized device successfully emulates key synaptic functions, including short-term plasticity (STP), long-term potentiation (LTP), and spike-timing-dependent plasticity (STDP), demonstrating strong potential for neuromorphic computing applications.</p> Graphical abstract <p>Ca²⁺ doping substantially enhances the device consistency and synaptic properties of Cu_xO thin-film devices. Synaptic simulation and pattern recognition experiments further demonstrate their potential for brain-inspired computing applications.</p> <p></p>