Abstract: According to the classical fiber's statistical strength and some hypotheses,the statistical constitutive models of the rate-sensitive fiber and fiber bundle are set up,and the corresponding constitutive equations are deduced.The method to determine the mechanical parameters in the constitutive equations of the rate-sensitive fiber by the tensile impact test of the fiber bundle are proposed from such models.The tensile experiments of the E-glass fiber bundles are performed under the strain race of 10^-4-10⁸ l/s in order to examine the validity of the test models and its test method. The test results and its analysis show that the hypotheses of the models are correct an d the test method is practical. Such models explain successfully the mechanical behaviors of fiber under the strain rate of 10^-4 1.1×10⁸ l/s.