Abstract: A visco-elastic model for fiber reinforced composites based on standard linear solid model was developed. Its governing equation as well as the formulae of relaxation modulus and creep compliance was deduced. The finite element method analysis testified that this model has a good accuracy. By virtue of this model, the effects of fiber geometric properties on relaxation modulus and creep compliance of the composite were also investigated. The results reveal that creep compliance of the composite is in a linear relation with fiber-matrix length ratio (FMLR). When fiber-matrix radius ratio (FMRR) exceeds a critical value, relaxation modulus and creep compliance change only slowly, and the critical value decreases with the increasing elastic modulus of fiber. Moreover, if fiber-matrix modulus ratio is quite large, fiber reinforcement-coefficient and compliance-coefficient are time independent.