Abstract: High pressure staged combustion liquid oxygen kerosene engine is used in the boosters of Long March 5 (LM-5, CZ-5) launch vehicle. The engine adopts high pressure staged combustion cycle, and has the characteristics of high performance, self-starting, wide range of thrust and mixing ratio adjustment and compact structure. In this paper, the development history and technical scheme characteristics of LM-5 launch vehicle’s liquid oxygen kerosene engine are reviewed. The key technologies in the development of the parallel mode engines are analyzed emphatically, such as self-starting ignition technology, large time difference asynchronous shutdown technology and low frequency characteristics of structure in YF-100 engine single mode and two-engine parallel mode. The improvement of performance enhancement, structure lightening, reliability growth and full mission environmental adaptability for YF-100 engine, as well as the demand for high-precision online fault diagnosis system for liquid oxygen kerosene engine, is proposed.