In this thesis, we have mainly illustrated the hydropower engineering and power transmission technology in China. Through the comparison between the greatest hydro power station, the Three Gorges Dam, with some other great stations, we have obtained the hydro power technology is now quite mature and efficient in practice with 90% conversion rate. Afterwards, we have explained the procedures of how the kinetic energy and/or gravitational potential energy are transformed to electric power. And meanwhile, this thesis gave the detailed introductions with plenty diagrams to elaborate the working status of Three Gorges Dam and also the working theory of turbine. At last, this thesis showed the distributions of the constructed grids, and indicated the main high voltage AC and DC transmission lines which connect different grids in mainland of China. This huge project has covered over 1 billion people. Besides, we have given some suggestions for decreasing the damage from the earthquake and freezing to grids. And this thesis is ended with our analysis and conclusions for what we have studied above.