Abstract: To address the limitations of traditional hydraulic accumulators, such as low energy storage density, significant pressure fluctuations, and difficulty in constant-pressure regulation, a novel linkage-spring constant-pressure accumulator is proposed in this work. The accumulator integrates a hydraulic piston cylinder with an inline crank-slider mechanism and an offset crank-slider mechanism to form a constant-force mechanism. Energy is stored through spring compression, enabling near-constant hydraulic pressure output across the piston stroke. In the mechanism design, rod parameters are optimized to maintain a constant force at the slider end, while an adjustable crank is innovatively introduced to facilitate convenient regulation of the constant-force magnitude. A nonlinear dynamic model is established to analyze the effects of oil stiffness, damping, and friction characteristics on pressure stability. Simulation results demonstrate that stable constant-pressure output is maintained even after accounting for nonlinear factors. Finally, experimental validation is performed under varying spring stiffnesses and installation positions. The results confirm robust operational performance of the accumulator, providing a new solution for enhancing the energy storage efficiency of hydraulic systems.