Abstract: With the increasing use of unmanned aerial vehicles, unmanned surface vessels, and unmanned underwater vehicles in maritime reconnaissance, communication relay, coordinated penetration, and terminal strike missions, high-value maritime targets are facing asymmetric threats characterized by low observability, multi-domain coordination, low cost, and saturation attacks. The focus of maritime counter-unmanned protection has shifted from intercepting individual platforms to identifying, degrading, disrupting, and sustaining against unmanned threat mission chains. This paper reviews the development and key technologies of maritime multi-domain counter-unmanned protection systems. First, the types, application scenarios, and challenges of maritime unmanned systems are analyzed. Then, key technologies are summarized from four aspects: reconnaissance and early warning, jamming and deception, strike and neutralization, and platform protection. Finally, a mission-chain-oriented protection framework based on reconnaissance, jamming, strike, and protection is proposed, and future trends are discussed in cross-domain fusion, soft-kill and hard-kill coordination, cost-effectiveness balance, and system-level verification.