The invention provides an alkane chiral allylic thioether compound and a preparation method thereof. The compound is an optical pure compound having the following structural formula, wherein * represents a chiral carbon atom; R1 represents groups optionally selected from alkyls of C1-C16, N, O or S-containing heterocyclic groups of C4-C10, and N, O or S-containing heteroaryls or aryls of C4-C10; and R2 represents groups optionally selected from alkyls of C1-C16. The alkane chiral allylic thioether compound having an optical activity, is synthesized by reacting allylic carbonates and sodium alkyl mercaptan by using a transition-metal iridium complex as a catalyst, with high regioselectivity and high enantioselectivity. Compared with the method of the prior art, the method has the advantages of easily available catalyst, high catalytic activity, mild condition and wide application scope of substrates.