In this paper the results of study on the nonlinear and lasing output characteristics of an organic polymer system, are presented. To describe the dynamics of light field in the medium, the forced oscillation model of optical multi-stable and lasing system are used. For the matter model, the material with the conjugate structure, such as polydiacetylenes which energy structure can be reduced to a three-level system considered; meanwhile the approach of efficient susceptibility is used to deduce the nonlinear susceptibility. Under these conditions, theoretical analyzing and numerical simulation shows that the system appears special output characteristics and dynamic behaviors, also instability, responding to the incident signal, especially when it satisfies both the gain condition of amplifying and that of multi-stable states. Further, the relationship between the detuning and the conditions of light amplification in this system are given out. Moreover, we find the detuning condition can describe and generalize the "frequency pulling effect", in proper situation.