The connection error of secondary winding will seriously affect the transformation ratio characteristics of tap type current transformer． The influence regulation of different loads connected to the non － working connection on the transformation ratio of tap type current transformer has not been studied in depth，which leads to the inaccurate analysis on the changes of transformation ratio of tap type current transformer when the non － working connection is connected． Theoretical analysis and test are used to analyze the influence of different loads connected to non － working connections on the transformation ratio characteristics of tap type current transformer． The results show that the ratio of primary current to working winding current has a positive linear relationship with the load connected to the non － working connection，and the ratio of primary current to non － working winding current has an inverse relationship with the load connected to the non － working connection． The results can provide a technical reference for power stealing analysis of current transformer when the non － working connection is connected．