The invention belongs to the technical field of alloy and particularly relates to a copper alloy wire and a preparation method thereof. The copper alloy wire takes copper as a matrix, and the added elements are tin or tin and at least one of titanium, magnesium, silicon or boron. The preparation method comprises the following steps: preparing a copper alloy rod from copper alloy liquid through a leading rod, performing necking processing, performing recrystallization and heat treatment, sequentially performing big pull, medium pull and small pull and preparing the copper alloy wire. The copperalloy wire is easy to thin, high in tensile strength and high in electrical conductivity, and can meet demanding application in the fields of a coaxial wire, a wire for automobile lightweight and a wire for a minitype loudspeaker coil; and the application prospect has high expectability and the cost is low.