A 200 MWe circulating fluidized bed (CFB) boiler with three cyclone separators was built in Inner Mongolia in China, and tests were carried out with the coal combustion process. The objective of this research is to investigate the effect of primary (secondary) air flow rate on the combustion process and the effect of multicyclone separator arrangement on solids circulation characteristics. Temperature and pressure drops at different positions in the boiler chamber and cyclone separator diplegs were measured. On the basis of the measured temperature and pressure, heat flux and solids void fraction distribution in the chamber are derived and analyzed. The profiles of temperature, pressure, heat flux, and solids void fraction along the height of the CFB boiler chamber and in the dipleg of cyclone separators at different operation conditions are given and discussed. The secondary air penetration depth in the dense area was tested at different operation conditions, and the effect of secondary air on the combustion process has been investigated. The preliminary test results indicate that the solid distribution in the three parallel cyclone separators is nonuniform and future research is necessary to optimize the arrangement of multicyclone separators for large scale CFB boilers. Key issues on superhigh pressure CFB boiler design, scaling up of CFB boilers, and further work on computational fluid dynamics (CFD) simulation for hydrodynamic behavior in the CFB boiler and cyclone separators are given at the end of this paper.