This paper proposes a pulse-width-amplitude-modulation (PWAM) method for a boost-converter-inverter system in electrical vehicle motor drive application. A 1kW prototype has been built and tested. By using this method, a 87% switching loss reduction, a two times power density increase, and 30% cost reduction can be achieved. It is also demonstrated that it posses less harmonic distortion than SPWM at only 1/3 switching frequency of the latter one. The maximum overall system efficiency reaches 96.7% at 1kW. The whole system power density is 2.3kW/L or 0.5kW/b. As a result, a high efficiency, high power density, high temperature and low cost boost-converter-inverter system can be achieved to use in electrical vehicle motor drive.