The invention relates to a thermal plasma device for incinerating marine garbage, which comprises a feed system, an incinerator, a plasma system, a secondary combustion chamber, a blast blower, a heat exchanger, a desulfurization and dust removal tower, a draught fan, a first water pump, a quench cooler, a second water pump, a tapping device and an automatic control system. The invention adopts a transferred-arc and non-transferred arc dual-purpose direct-current plasma generator as an incineration heat source, which not only can make full use of a shipborne dynamic power supply (or an accumulator battery) but also can use a non-transferred arc in the initial stage of incineration and adopt the working mode of a transferred arc after a molten pool is molten. Compared with a single non-transferred arc operation mode, the heat transmission property is better, the incineration efficiency is higher, and more energy is saved; in the invention, the secondary combustion chamber adopts plasma heating in a similar way, and the condition that new pollution is generated in the treatment process of secondary combustion is avoided; and by high temperature generated by the plasma generator adopted by the invention, the temperature of the molten pool exceeds 1500 DEG C and is sufficient to enable inorganic substances, slag and heavy metal to be fused together, the inorganic substances, the slag and the heavy metal are solidified in a neutral vitreous body and are not easy to precipitate, the treatment of the garbage is finished by one step, and the thermal ignition loss rate is less than 3%.