In this study, we establish a car model which better resembles a real car and compare with the simplified car model as a reference. When taking the circular polarization antenna into consideration, we need the refined car model in the simulation. Besides, TPMS antenna measurements are conducted and the results are compared with the simulation to verify the accuracy of our simulation. The result of the simulation shows that the signal cannot be received when TPMS antenna is mounted on the rear tires. Proper solution is suggested to alleviate this problem. Due to the limitation of the measurement environment, we consider using scale-sized car model for the measurement of the antenna radiation pattern. Also, we compare the radiation pattern in the scale-sized car model with that in the full-sized car model. For the measurement of the vehicular antenna, we find that using the scale-sized car model for the preliminary estimation of the antenna radiation pattern is feasible and practicable.