The possible activated slip systems and slip traces of pure coarse-grained magnesium were investigated during cyclic deformation at room temperature. Results show that numerous criss-cross slip traces are observed on the surface of the specimens after cyclic loading. Based on the results of a combinatory analysis for the unit cell orientation and direction of the slip traces, it is determined that the criss-cross slip traces are formed by the intersection of the basal slip traces in the former matrix and the subsequent {} twinning area during the reversed cyclic loading. Moreover, the most likely pyramidal slip mode is the sliding of <> pyramidal dislocations on {} pyramidal planes, while the basal slip traces are denser than the pyramidal slip traces, suggesting that there is limited pyramidal slip activity.