Abstract: The Millikan oil-drop experiment is one of the classic experiments in university physics，and the

elementary charge can be calculated by experimental data processing. The experimental methods used by each university

are basically identical，but the experimental data processing methods are various. The data processing combined

with multiple methods is put forward to reduce the error caused by the data processing method，in which the

data is pre-processed by grouping and processed by the least square method based on graphic method and the result

shows that the error is significantly reduced. The ideas in this paper confirmed by five teaching classes are feasible

and valid，which can be applied and promoted in actual teaching.

Key words: Millikan oil-drop experiment, reduce error, graphic method