Investigation of boron particle agglomeration ignition and combustion in secondary chambers is very important for increasing the capabilities of ducted rockets. By experimentally mimicking ducted rockets, boron particle agglomeration ignition and combustion in secondary chamber flow field was investigated. The ignition and combustion processes, flame constructions and size changes of boron particle agglomeration were analyzed with the image processing techniques of high speed flame and the measurement results of flow field parameters. The effects of gas temperature and oxygen content on ignition and combustion of boron particle agglomeration were acquired. The analysis result of residue indicates that the particle size changes little and the gas may get into the boron particle agglomeration and react with boron particles.