The invention provides a redundancy protection method for an isolated two-stage chain-type energy storage system. The redundancy protection method comprises measures in both hardware and software, wherein in the aspects of hardware, an additional standby unit is added to each phase of an isolated two-stage chain-type converter to replace a breakdown unit in the isolated two-stage converter; in the aspect of software, through increasing the DC-side voltage of a two-stage isolated full-bridge converter, in case of more serious failure of the chain-type converter, redundancy protection is further provided, and final redundancy protection is provided through improving the modulation ratio of an H-bridge of the chain-type converter. The redundancy protection method provided by the invention can achieve redundancy protection of the isolated two-stage chain-type converter in a layered manner through hardware and software, so that normal operation of the chain-type converter in case of failures of some units is effectively guaranteed, the reliability of the converter is improved, and meanwhile, abundant time is provided for on-line maintenance of the isolated two-stage chain-type converter.