Amorphous GaSb thin film have been prepared by rf-magnetron sputtering. The effects of ther mally-induoed phase change of the film on its optical properties and miorostruoture have been studied systematically. It is found that amorphous GaSb thin films change to polycrgstalline state with cubic structure (α0 = 0.6095 nm) around annealing temperature 270℃, and the optical gap changs from 0.7(eV) to 0.94 (eV) after the phase change. The cauve of GaSb thin film resistance versus annealing temperature is measured by fourprobe method. And write-once recording properties and laserinduced phase change of the GaSb thin film have been studied.