Recovery behavior of 20% plastically deformation of casting AlSi11.35Mg0.23 in various stages of isochronal annealing has been investigated by positron Lifetime (LT). The experimental results show that the positron mean lifetime is a function of annealing temperature. Lifetime of the positron annihilating in perfect lattice is 187.3ps and in 20% deformed is 229.8 ps. There are two regions in the isochronal annealing, one of them relating to the point defect and the other to the dislocation. The activation enthalpy for the dislocation is calculated from the isothermal study in the dislocation region from (575-675) K by slow and fast cooling as 0.16±0.02 and 0.53±0.06 eV respectively.