This paper presents a high-performance test bench for Mega Watt (MW) level high-speed machine and MW level 10 kV rectifier with 333 Hz fundamental frequency. It is based on AC pump back topology under the limit of 400 kW grid power capacity. In this paper, the overall structure of the test bench is introduced. Key features those enabling high-speed high-power loop test are analyzed in details. First of all, the mechanism of circuit breaker arc reignition and cable derating caused by high frequency are quantitatively analyzed and a guideline for the design and installation practice for these components is formed, which is different from the guideline at low frequency. Next, based on the multi-level real-time control system which realizes the monitoring and control of the large scale test bench, a multi-time scale protection system is designed for complex faults and failure modes. According to a step-by-step decoupling verification strategy, the DUT and the pump back test bench are both successfully built and experimentally validated at their rated operation points.