When the modular multilevel converter (MMC) arms do not have redundant sub-modules, the fault of the sub-modules decreases the output voltage capability of the faulty phase, which leads to the unbalanced output line voltage of the MMC. In order to restore the post-fault output line voltage characteristics of the no-redundant MMC and improve the utilization rate of the non-faulty arm's sub-modules, a sub-module fault-tolerant control strategy which is suitable for non-redundant MMC is proposed based on neutral point transfer (NT) and direct current component injection (DCCI) control. The fault-tolerant strategy adjusts the phase angle of the three-phase voltage through NT control for ensuring the balance of the output line voltage. In addition, a three-stage optimal DCCI amplitude calculation method is proposed. Compared with the existing methods, the optimal amplitude DCCI further improves the utilization rate of the non-faulty arm's sub-modules and increases the output line voltage amplitude. A three-phase MMC simulation model based on the PSCAD/EMTDC platform is built, and the effectiveness of the proposed no-redundant fault-tolerant control strategy is verified through the simulation results.