<p>Semi-active suspension systems have emerged as a pivotal technology for enhancing vehicle ride comfort and handling stability, due to their controllable damping properties and energy-efficient operation. Owing to its suboptimal performance, the mixed sky-hook and ADD (SH-ADD) method has become the representative control method in semi-active suspension research. However, the phase difference between the sprung mass acceleration and the relative velocity causes faulty switching events in the frequency range selector, limiting its performance in the targeted frequency range. To address this, the phase-corrected SH-ADD (PC-SHADD) semi-active suspension control method is proposed, featuring a phase correction frequency-dependent damping switching control. The advantage of it lies in replacing the acceleration of the sprung mass with the relative velocity of the suspension at a smaller phase, reducing the misclassification rate of the frequency range selector by 48.1% under frequency-swept sinusoidal excitation. Comprehensive simulations and hardware-in-the-loop (HIL) experiments, utilizing a commercial CDC damper, validate the superiority of the proposed method. Under a standard speed bump impact, simulation results show that PC-SHADD reduces peak sprung mass acceleration by 32.0% compared to a passive system—a substantial improvement over the negligible 0.8% offered by SH-ADD—without demanding additional suspension travel. Under stochastic random road excitations, PC-SHADD consistently improves ride comfort, reducing RMS acceleration by an average of 21.2%. These findings are robustly corroborated by HIL tests, where PC-SHADD achieved a 28.7% reduction in peak acceleration over the speed bump and a 17.1% RMS acceleration reduction on a Class B random road, outperforming the baseline SH-ADD in both transient and stochastic scenarios. The performance gains are concentrated in the critical 0.7–7 Hz frequency band, confirming the enhanced accuracy of the proposed phase correction switching logic.</p>