Iridates are of current great interest for their entangled spin-orbital state and possibly exotic properties.In this talk, we demonstrate, using density functional calculations, that the hexagonal spin-chain materials Sr3MIrO6 (M=Ni, Co) are an iridate system in which the spin-orbit coupling (SOC) tunes the magnetic and electronic properties.The significant SOC alters the orbital state, the exchange pathway, and thus the magnetic structure.Our results clarify the nature and the origin of the intra-chain antiferromagnetism of Sr3MIrO6 and well account for the most recent experiments.