Abstract: To investigate the operational stability and displacement deviation characteristics of the flexible-connected control rod hydraulic drive system (CRHDS) under pressure disturbances, this study first analyzed the composition and working principle of CRHDS, then constructed a full-scale cold-state experimental test rig. A series of systematic experiments were designed to independently regulate key parameters such as inlet pressure and outlet pressure, focusing on the effects of the electromagnetic clutch’s operating state, the elastic properties of the connecting rope, and the type of pressure disturbance on the displacement deviation of the control rod assembly. The experimental results indicate that the engagement and disengagement states of the electromagnetic clutch have no significant impact on the system’s anti-interference performance. The system can independently respond to and dynamically correct pressure disturbances relying on the closed-loop self-regulation mechanism formed by the piston and throttle disc. The elastic property of the connecting rope is a core factor determining the system’s anti-interference performance. The displacement deviation decreases significantly and monotonically with the increase of the rope’s stiffness, so materials with greater stiffness should be prioritized in the selection of connecting ropes for flexible-connected systems. When the system encounters pressure fluctuations within the range of 0.1-0.8 MPa, it can achieve force balance reconstruction and self-stabilizing regulation through the dynamic adaptation of the throttle port gap. Specifically, under positive pressure disturbance, the control rod assembly shows an upward deviation with a range of 0.08-0.5 mm; under negative pressure disturbance, it exhibits a downward deviation ranging from 0.1-0.52 mm. The displacement responses under both disturbances are within a controllable range, verifying the system’s excellent adaptability and self-stabilizing capability to pressure fluctuations. This research provides reliable experimental data and theoretical support for the structural optimization, component selection, and performance improvement of CRHDS.