Sapphire single crystal fibers possess structural advantage of high melting point, stable physical and chemical properties of sapphire and large length-to-diameter ratio of fiber, making them widely studied in the fields of high temperature sensing and radiation detection. In this paper, high quality sapphire single crystal fibers were successfully prepared by laser-heated pedestal growth (LHPG) method with a minimum diameter of 50 μm and extremely high flexibility. On this basis, the influences of crystal orientation, crystal diameter, annealing temperature on the stress distribution and mechanical properties were systematically studied. The tensile strength of the prepared sapphire fiber exceeds 3 000 MPa, showing its excellent mechanical properties.