The hydrogen storage capacities and pressure-composition isotherms of TiFe + La and TiFe + Mm alloys were measured by exhausting water method. The effect of La and Mm on the activation characteristics of the alloys was studied. It was shown that the activation characteristics of the alloys could be improved greatly and the alloys were activated near the room temperature when the quantities of La or Mm in the alloys were greater than 4 wt% under our experimental conditions. However, La or Mm did not enter the crystal lattice of TiFe. They presented in the alloys in the form of a second phase to purify the alloys. The hydrogen storage mechanism mainly depends upon the intermetallic compound TiFe. The formation enthalpies of the hypothetical hydrides TiFeLayH1.0, were also calculated after Miedema's formulae and compared with the experimental results.