Deformation twinning and dislocation slip are the most important mechanisms in determining the plastic deformation behaviour of Mg. In this project, the interactions between two types of twins, including (10-12) extension and (10-11) contraction twins, and three types of dislocations, including < a >, < c > and < c+a > type dislocations, are studied using molecular dynamics simulation. The focus of this work is to establish the formation condition for different types of interaction products, the characters of the products, the subsequent interaction between the migrating twin boundary and the resultant lattice defect structure in the twin crystal.