Abstract: Magnesium and its alloys have attracted extensive attention due to their favorable mechanical properties, such as low density and high specific strength. The detwinning process of 10\bar 12 tensile twins subjected to periodic loading is one of the microscopic mechanisms of fatigue damage in magnesium and its alloys. Moreover, self-interstitial atoms (SIAs) widely exist as a typical kind of point defects in metals. The migration, aggregation, and interaction with other defects, of SIAs affect the metal mechanical properties. In this work, molecular dynamics simulation was employed to study the detwinning process of 10\bar 12 twins under shear loads in magnesium, focusing on the interaction between the twin boundary and SIAs in the detwinning process. A simulation system containing two coherent twin boundaries (CTBs) with periodic boundary conditions applied along the two in-plane directions was adopted. The classic embedded atom method (EAM) interatomic potential developed by Liu et. al was used for simulation accuracy and comparison with other studies. The simulation results show that the SIAs are absorbed by the CTBs and migrate along with them. The absorbed SIAs can be released with the disappearance of the CTBs during the detwinning process. By the SIA adsorption and release, detwinning process will result in a more concentrated SIA distribution. The simulation results reveal that SIAs will be adsorbed by CTB if the distance between the CTB and SIA is less than 0.752 nm at 0 K and 3.59 nm at 273 K. The energy barrier of the adsorption process is also obtained using the nudged elastic band (NEB) method. The SIA spatial distribution changes after the SIA interactions with CTB in detwinning process. Given that the crystal defects such as dislocation loops can be induced by the dense distribution of SIAs at a long timescale, this study clarifies the fatigue mechanical properties of magnesium and magnesium alloys subjected to periodic loading.