The multiline thru-reflect-line (TRL) calibration algorithm model is used to determine the error sources and uncertainties for on-wafer S-parameter measurements, and the uncertainty source is presented in a diagrammatic form. The quantitative contribution of each input error source to the S-parameter of the device under test (DUT) is obtained through the Monte Carlo method. Through analysis, it is found that the dynamic accuracy of the vector receiver as an ignored source of uncertainty makes a significant contribution to the amplitude of transmission coefficients and large reflection coefficient of the on-wafer S-parameters. Finally, the influence of dynamic accuracy measurement error on the DUT with different reflection coefficients is studied.