Large and super-large scale natural gas turbo-expanders in China are all imported. Based on the super-large scale LNG project of a company, this study completed the key technologies research on the projects super large scale natural gas turbo-expander such as the high-efficiency compressor with both large flow rate and low pressure ratio, the vibration mode analysis of high-power impeller, the high-power torque transmission structure design, the rotor thrust balance scheme, the bearing development and so on. The company designed and built a prototype of super-large scale natural gas expander-compressor unit based on the research findings. The simulated performance test results of the prototype show that the performance of this expander-compressor unit has reached the top-level achieved in China. This research and development results lay a strong foundation for promoting the locally designed and built major technical equipment such as large and super-large scale natural gas turbo-expanders.