Peculiarities of the uncertainty determination in case of vector values measurement are analyzed. Analysis shows, that in case when both parameters of vector value are significant, appear correlation between these two measured parameters, caused by imperfection of the measuring instrument and uncer-tainty of both parameters of used standard. This correlation has to be determined and taken into account during the uncertainty determination. On the example of inductivity unit reproduction analysis show that neglecting of this fact could led to incorrect uncertainty determination.