A self-propelled semi-submersible type maintenance vessel is provided with an engine room system and a propelling system, wherein the two sets of systems are respectively and independently controlled. A main deck is a flat and wide deck, and support buttresses and a crane running rail are arranged on the main deck. A crane is arranged on the rail. A water tight side tank, a steering engine room, a chain locker, an engine room, an oil tank, a water ballast space, a fresh water tank, a tool and a machining workshop, an oxygen room, an acetylene room, a waste material recycling room, a salvage equipment room, a spare part warehouse and a goods transfer device are arranged below the main deck. A forecastle is arranged. Ballast water is also loaded in the water tight side tank, and the total capacity of the water ballast space can enable the main deck of the self-propelled semi-submersible type maintenance vessel to dive 1-30 meters under water. The self-propelled semi-submersible type maintenance vessel has the advantages of having an offshore maintenance function, being capable of maintaining on the sea, capable of quickly sailing, diving, floating, loading and unloading, having functions salvation salvage and special heavy bulk transport, and being capable of being used for loading and transporting large-scale marine equipment or engineering structure works which are oversized, overweight and indivisible.