The present work attempts to investigate the influence of mechanical activation on structural and microwave absorbing properties of high titanium slag. Microwave absorbing properties of high titanium slag were investigated by using microwave cavity perturbation technique and the digital signal processing technique. The crystal structures and the molecular structure of high titanium slag before and after mechanical activation were also analyzed using XRD and Raman spectra, respectively. The results of microwave absorbing properties indicated an optimum mechanical activation duration of 12 h. The results of XRD and Raman spectra showed that Ti2O3 is transformed partially from Fe3Ti3O10 under moderate mechanical activation, which can be better used for the production of synthetic rutile. The results demonstrate effectiveness of mechanical milling as pretreatment process for production of high titanium slag. (C) 2015 Elsevier B.V. All rights reserved.