Abstract: The characteristics of grounded high titanium slag during the hydration process were discussed comparing with grounded low titanium one. The mineral composition, hydability and hydrating characteristics of grounded high titanium slag, and the hydration product were analyzed by means of X-ray diffraction analysis, SEM, EMPA, DTA separately. The results demonstrate that the hydaulic activation index of high titanium BF slag is 77.4% while that of slag with low titanium is 108%. The high titanium slag has the same hydration product as the low titanium slag and the portland cement. However, the amount and the crystallinity of hydration product in the high titanium BF slag are obviously lower than that in the low titanium slag. This means the high titanium slag has low hydaulic activation index.