This paper presents the on-chip transmission line modeling and applications to circuit design at millimeterwave (mm-wave) frequencies. The microstrip model of circuit simulators benefits in fast calculations of the characteristics of microstrip lines. As the structure of on-chip microstrip differs from the modeled structure, two key parameters of the microstrip model need to be modified for the different electromagnetic (EM) behavior according to the measured microstrip line. With proper parameters, the traditional transmission line model is able to accurately predict the real characteristic of on-chip microstrip lines without time-consuming EM simulation. A mm-wave microstrip line filter and a single-stage cascode low noise amplifier (LNA) are fabricated to verify the model. All passive components for input/output matching networks and bias networks are onchip. The LNA takes the supply voltage and dc current of 1.4 V and 10 mA, respectively. A gain of 3.8dB and an input/output return loss of 8.5/7.0dB are measured at 60.3GHz. The simulation results in both circuits are in good agreement with measured data.