This article describes the results of designing a microwave wideband voltage-controlled oscillator (VCO) by using electromagnetic (EM) simulation. EM simulation is carried out in AXIEM, which is included in AWR Design Environment of National Instruments (NI AWR DE). The main features of VCO design using AXIEM are considered. The study analyzed the comparative possibilities of electromagnetic and circuit simulation with the help of NI AWR DE. Analysis was based on the experimental studies of the developed oscillator. It is shown that EM analysis can significantly improve the accuracy of modeling compared with design in Microwave Office (MWO, system of circuit simulation).