Abstract: The phenomenon of stochastic resonance in an overdamped linear oscillator subject to multiplicative colored noise is investigated. An explicit expression of the output amplitude gain (OAG) of the oscillator is obtained based on linear system theory. Results show that the OAG is a non-monotonic function of the strength, and the correlation rate of colored noise as well as the external field frequency. By choosing appropriate parameters of the noise and the oscillator, the OAG of the noisy oscillator can be larger than that of the noise-free oscillator. Meanwhile, the effect multiplicative noise and the parameters of the oscillator on the OAG are discussed.