The invention discloses a direct-current converter station based on a bipolar structure. The direct-current converter station consists of two convertor units connected in series, the serial connection point of the two convertor units is grounded by a neutral bus, and each convertor unit consists of a plurality of MMC (Modular Multilevel Converter) which are connected in series and in parallel. With the structure, when direct current fails, only the fault pole is affected, and a perfect pole is hardly affected, so the system reliability is improved; meanwhile, according to the direct-current converter station, the neutral bus is led out to be grounded, the stage construction and capacity-increasing construction of a system can be conducted easily, and a single pole is firstly put into operation, then double poles are put into operation, so that investment benefits can be obtained early; and simultaneously, the neutral bus is grounded by a grounding pole guide line to provide a current backflow access to a system in a single-pole ground loop operation mode, and when the system is in balance operation, the grounding current is extremely low.