Disclosed herein is a core-shell spinel cathode active material for lithium secondary batteries. The core portion of the active material is made of a spinel manganese-containing material substituted with fluorine or sulfur, having 4V-grade potential and showing low-cost and high-output characteristics, and the shell portion, which comes into contact with an electrolyte, is made of a spinel transition metal-containing material, having excellent thermal stability and cycle life characteristics and showing low reactivity with the electrolyte. Thus, the cathode active material shows significantly improved cycle life characteristics and excellent thermal stability.