The present invention relates to an active material for a lithium secondary battery, which includes a secondary particle formed by agglomeration of primary particles which include a lithium titanium composite oxide represented by Formula 1 or Formula 2, wherein a pore volume is in a range of 0.001 cm3/g to 0.05 cm3/g, and a method of preparing the same, wherein the active material for a lithium secondary battery according to the present invention may maintain an adequate pore volume even during rolling, because strength of the secondary particle is improved by controlling a particle diameter of the primary particle by introducing a metallic element.