A direct current voltage compensation method for a parallel mixed-type multi-level converter. The converter is a three-phase power transmission structure, the three-phase power transmission structure consisting of a parallel-type single-phase structure series connection. A parallel-type single-phase structure consists of an H bridge full-control device structure (2) and a sub-module cascade structure (1) connected in parallel, the H bridge full-control device structure consisting of a cascade structure having four full-control devices (S1-S4), the sub-module cascade structure consisting of a half-bridge sub-module series connection. The compensation method comprises: an isolation time is added during a converter normal operating mode, the sub-module cascade structures are freely controlled in the isolation time, a required compensation voltage is thereby outputted, compensation of a direct current voltage shortfall is implemented, and a compensation ratio in the three-phase power transmission structure adjusts a three-phase distribution ratio according to requirements. The compensation method effectively implements direct voltage fluctuation compensation of a parallel-type mixed new topology, and is particularly suitable for voltage compensation in the case of an alternating current system fault.