Effective control of dislocation climb is of fundamental interest and practical importance in tuning the mechanical and electronic properties of semiconductors. However, it remains a big challenge due to the lack of a clear understanding of its inherent mechanism, in particular, in the nitride semiconductors. In this Letter, the atomic-scale climb process of a single dislocation in GaN is observed for the first time, which undergoes an alternating five- and nine-atomic-ring transformation. Combined with first-principles calculations, we reveal that the jogs exhibiting asymmetric atomic configurations play an unexpected role in determining the different dislocation climb behaviors in GaN. Interestingly, tuning the Fermi-level position by electroactive dopants can selectively generate different species of jogs, which can consequently manipulate the dislocation climb behaviors and dislocation dissociation in a controllable way. Our findings not only highlight the significant role the asymmetric jogs play in the dislocation climb in nitrides, but also suggest a clear routine to control dislocation dynamics in semiconductors.