The output voltage of the force sensor is an important parameter to be measured in the experiment ofmeasuring liquid surface tension coefficient by pulled off method. lt is very important to understand theexperimental principle and improve the accuracy of the experimental measurement.lt focuses on the study of thestate of the ring and the liquid film ,the change of force and the change of voltage with the height of the liquidhilm carried out by the ring during the measurement process,based on the experimental principle of measuringliquid surface tension coefficient by traditional pulling method.Finally,the selection of voltage measurementpoint in the experiment is clarified, the theoretical analysis formula is modified and the experiment ayerification is carried out.The verification results show that when the sling is in the critical state , the sensoroutput voltage U, should be selected as the maximum value of the voltage reading,which is more consistentwith the experimental principle.Moreover,the quality of the liquid film can not be ignored and should beincluded in the theoretical analysis and calculation to get more accurate results.The research results canprovide analysis ideas and reference for the course teaching of this experiment.