Low energy discharge is an intermittent spark discharge. Low energy discharge of ultra-high voltage DC voltage divider will cause sudden voltage sag or jumps，seriously affecting safe and stable operation of power grid. In this paper，the low-energy discharge phenomenon of ±800kV DC voltage dividers is analyzed，the internal short circuits to ground is simulated by using RTDS simulation test. The cause of the fault is analyzed through such works as disassembly，testing，and detection and preventive measures are proposed，which provide reference for preventing and eliminating faults and abnormalities of ultra-high voltage DC voltage divider and accumulating valuable experience for safe and stable operation of ultra-high voltage DC equipment and power grid.