Abstract: Light burned MgO is an important chemical raw material. With the increase of the requirements for high-efficient utilization of resources， the process of preparing MgO by calcination of powdered magnesite gradually received attention. Fluidized bed with high efficiency heat and mass transfer is one of the most ideal reactors for powder calcination. Magnesite flotation concentrate in Liaoning were regarded as the research object， and the basic experimental study of fluidized calcination was carried out. Through XRD phase analysis， citric acid activity test and SEM analysis， the phase change， microscopic morphology and MgO activity of two kinds of samples (120~200 mesh and 200~300 mesh) under different calcined temperature and time were discussed. The results showed that: ① With the increase of calcination temperature and the extension of calcined time， the contents of MgO increases and the diffraction peak of MgO becomes narrower and stronger. The phase transition law of samples with granularity between 200 and 300 mesh is basically the same as that of the samples with granularity between 120 and 200 mesh. The particle size has little effect on the decomposition process. ② The suitable calcination conditions of samples with granularity between 120 and 200 mesh， and 200 and 300 mesh are calcined at 800 ℃ for 10 min and 850 ℃ for 5 min， respectively. At this time， the calcined product MgO activity is the highest， and the citric acid color development time is 38 s and 21.5 s， respectively. There is a great difference between the two kinds for suitable calcination processes. In the industry， the residence time of calcined materials with different particle sizes should be controlled to avoid overburning and underburning. ③ Particle size has little effect on the decomposition process， but has a great effect on the grain growth， thus affects the MgO activity. Compared with the samples with granularity between 120 and 200 mesh， the samples with granularity between 200 and 300 mesh has finer particle size， higher heat and mass transfer efficiency， stronger CO2 adsorption capacity on the surface， less lattice defects， and relatively fast grain growth rate， so the turning point of activity appeared earlier.

Key words: fluidization calcination, calcined temperature, calcined time, fraction, the phase transformation, magnesium oxide activity, micro morphology