Organic lightemitting diode (OLED) is a brand new display and lighting technology, utilizing the electroluminescence (EL) of organic molecules. One of the key issues impeding the commercialization of OLED is its lightemitting efficiency and operational lifetime. A tandem OLED consists of multiple electroluminescence (EL) units, connected by unique intermediate connectors. The current efficiency and lifetime of a tandem OLED with N EL units can be more than N times those of the individual OLED unit. Hence, tandem OLEDs provide a promising approach to fabricate highly efficient and long lifetime displays and solidstate lightings. The charge generation ability and charge injection of the intermediate connector in a tandem OLED determine the performance of the device. Meanwhile, the transparency and the optical path also have an impact on the light output. Therefore, both the electrical and the optical properties of the intermediate connectors should be considered during the design of tandem OLEDs. To capitalize on the advantages of tandem OLEDs, the manufacturing equipment should also be specially designed and developed. Here, we systematically introduce the advantages, design principles, and optimization of tandem OLEDs. Combined with the research and development of manufacturing equipment, we further elaborate the importance and urgency of establishing the OLED product chain in China.