Abstract: The 4 MV electrostatic accelerator consists of four parts, a high voltage system, an ion source and beam transmission system, a control system and a gas system. Some technical problems arose during the debugging of the accelerator. The ion source did not produce arc. The accelerator tube cracked. The control system was out of order. The transporting capacity of the charge belt degraded. The corresponding reasons were analyzed and some measures were adopted to solve the problems. The drawing voltage was raised to its predetermined position after the ion source produced arc and should be reduced to zero before turning off the accelerator. Transition flange was lathed and the accelerator tube was re-assembled. The control equipment at high voltage was shielded. TVS diodes were installed at th