Abstract: This paper studies the macro and micro states and thermal properties of calcium carbonate rocks such as limestone, calcite and iceland spar by X-ray fluorescence spectroscopy, differential thermal analysis to analyze the crystallinity and the degree of powder of these ore and the grain size and lattice distortion of the calcined lime. The conclusions are as follows: with the increase of mineral grains, the possibility of fragmentation increases； the decomposition temperature of calcite and iceland spar are similar to limestone, they can be used as slag former in converter, but their heat consumptions differ in decomposition process； four original stone are calcined in a muffle furnace at a rate of 10 ℃/min until temperature reach 820 ℃.The grain size of CaO is 61－85 nm, while the grain sizes of calcite and iceland spar with bigger original grains are smaller and have higher degrees of activity which is better for salg forming in converter.

Key words: limestone steelmaking, calcite, performance of powder, grain size；morphology