The invention provides an HVDC (high voltage direct current controller) and UPFC (unified power flow controller) system based on a modularized multi-level converter. The HVDC and UPFC system comprises converting devices (1, 2 and 11), grounding circuits (3 and 12) and a direct current transmission line (13). The UPFC is formed by the converting device (1) and the converting device (2). The HVDC is formed by the converting device (1) and converting device (11). The HVDC and the UPFC shares one converting device, so that cost and investment for engineering construction are saved, equipment utilization rate is improved, concentrated management and control are facilitated. The converting devices use the topological structure of the modularized multi-level converter, so that technical difficulty in component serial connection is avoided, split-phase control and modularization are facilitated, fault units can be bypassed through redundancy, operation stability of the devices is improved, on and off frequency of components is low, and device operation loss is low.