In this paper,we report a simple catalyst-free method for the synthesis of high-quality ultrathin ZnSe nanowires in a mixed ligand solution.By utilizing this method,we were able to tune the width and length of the as-prepared ZnSe nanowires from 1.5 to 3.1 nm and from 80 to 220 nm respectively through varying the reaction conditions(precursor concentration,ligand environment and reaction time).Among those conditions,we found that the concentration of oleylamine in the reaction system played a vital role in determining the size and morphology of the as-prepared ZnSe nanowires.The formation mechanism of those ZnSe nanowires were also intensively explored by tracking their morphological and optical variation during the reaction process.