Abstract: A method on the digital linear correction of (voltagecontrolled oscillator.（VCO) in the vehiclemounted radar RF frontend utilizing voltage segment is described in this paper， which is used to solve the nonlinear problem of the amplitude frequency characteristic of the VCO caused by the inherent nonlinear tuning characteristics of the varactor diode in the VCO. The linearity of the output of the VCO is improved by this method which combines with the advantages of analog and digital correction method. It improves the test precision and accuracy of the radar system as well.