Designing and fabricating Fe-based amorphous coatings with excellent wear and corrosion resistance as surface protection materials are essential to improve the service life of marine equipment. In this work, by adding 1 at.% Nb, a novel Fe34Ni20Cr20Mo5B4C4P12Nb1 high-entropy amorphous alloy with enhanced glass-forming ability and excellent corrosion resistance was designed. The Fe34Ni20Cr20Mo5B4C4P12Nb1 composition was adopted to prepare gas-atomized powders, which were then used as feedstock to prepare coatings using atmospheric plasma spraying (APS) technology with different input power. Higher spraying power was found to lead to denser coating, but more formation of oxides and lower amorphous content. The coating-35 kW input power exhibited the best corrosion resistance in 3.5 wt.% NaCl solution and high hardness of 519 ± 21 HV. The dry sliding wear rate of the coating-35 kW at 20 N and 20 mm/s was 8.3 × 10−7 mm3/(N m), and the friction coefficient of the coating was 0.17 and kept relatively steady throughout the sliding test. This work guided designing Fe-based high-entropy amorphous coatings from both the composition aspect and the coating preparation technology.