In order to avoid the insulating oil overflowing from the segregator and condensator and damaging the vacuum pump,the ABB vacuum oil filter must be closed and the overflowed oil cleared when reaching to the highest point.Then the machine is re-started and put into work.It is bound to affect the efficiency of the oil disposal.Aiming at the problem,the ABB vacuum oil filter is improved by assembling a small drainage equipment below the segregator and condensator.When the oil is overflowed,it is discharged from the segregator and condensator by the drainage equipment,guaranteeing the vacuum oil filter working uninterruptedly.The feasibility and higher efficiency of the improvement is proved by the practice in Nanyang UHV switching station.