The invention relates to the technical field of petrochemical engineering, and discloses a washing method and a washing system for a washing section of a vacuum tower. The washing method comprises the following steps: washing a fixed volume of oil drops with known components with different volumes of washing oil, and enabling the index of finally obtained vacuum wax oil to meet the requirement; washing the washing section of the vacuum tower with different volumes of washing oil, and enabling the index of the finally obtained vacuum wax oil to meet the requirement, wherein at the moment, the contents of heavy metals and residual carbon in residual oil drops can be accurately obtained according to the volume of the used washing oil, so that the volumes of the heavy metals and the residual carbon in entrainment can be accurately obtained; therefore, the contents of the heavy metals (such as Ni and V) and the residual carbon in a vacuum wax oil product can be accurately forecast, and the quality of the vacuum wax oil product is improved; the requirement of a downstream device on indexes of raw materials is met.