Single-mode optic fiber preform is a kind of single-mode optic fiber preform specially designed and developed for a series of special optic fibers. This series of preforms are prepared by in-tube chemical vapor deposition process, which has the advantages of good optical uniformity, good geometric uniformity, low hydroxyl group, high numerical aperture and so on. This series of performs can be specially designed according to the needs of users to meet the requirements of die field diameter, cutoff wavelength and bending sensitivity. This series of preform is widely used in the field of special optic fiber such as polarization-maintaining fiber, device optic fiber, inductive optic fiber and special purpose communication optic fiber.