In this paper, the preparation of rutile TiO2 powder from titanium slag by microwave-assisted activation roasting followed by hydrochloric acid leaching was investigated. The effects of the additive Na2CO3 on the crystal form, cell, crystallinity, phase transformation, surface functional groups and micro-surface structure of the calcined product were systematically studied using X-ray powder diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy. The results confirmed that the strongest characteristic Raman bands of rutile TiO2 and the weakest FT-IR bands of (CO3)(-2) were found when the Na2CO3 mass ratio was 0.4. Accordingly, the crystallinity for the product, namely short rod structure rutile TiO2 powder, reached its peak value of 99.21% with a corresponding average grain size of 43.5 nm. The excessive Na2CO3 was found to be disadvantageous for the crystallinity of the product, since it formed a coverage on the surface of titanium slag which prevented the oxidation reaction for the decomposition of anosovite. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.