In this paper, the authors report an investigation into the effects of the addition of amounts of H 2O and HCl on the spinnability and crystallizability of silica glass fiber by the sol–gel method. The spinnability of TEOS sol was dependent on the structure characteristics, which were controlled by the amount of H 2O and HCl. If a lineal structure (Si–O–Si) dominated in the sol, the sol exhibited excellent spinnability. The crystallizability was determined by structure characteristics of the Si–O–Si and the content of broken bond. It was easy to crystallize the SiO 2 glass fibers with a three-dimensional network structure and a low content of broken bonds. The optimum amount of H 2O and HCl with excellent spinnability and poor crystallizability was 1.5 and 0.03 mol ratio, respectively.