An anode active material for a lithium secondary battery and a lithium secondary battery are provided. The anode active material includes a carbon-based particle including pores formed in at least one of an inside of the particle and a surface of the particle and having a pore size of the carbon-based particle is 20 nm or less, and silicon formed at an inside of the pores of the carbon-based particle or on the surface of the carbon-based particle. Silicon has an amorphous structure or a crystallite size of silicon measured by an XRD analysis is 7 nm or less. Difference between volume expansion ratios of carbon and silicon can be reduced to improve life-span property of the secondary battery.