Abstract In this paper, on the basis of mesoscopic stochastic model of NO reduction by CO on single-crystal platinum surfaces, we report a novel effect of the external noise of reaction rate constant coupled to internal noise in stochastic resonance induced by external noise (SREN) or internal noise (SRIN). It is shown that the internal noise can enhance the SREN, and the external noise intensity for the SREN increases with increasing internal noise. However, the external noise can suppress the SRIN, and the suppressions nonmonotonously vary with the increasing external noise intensity. This result is different from the effect of the external noise of NO partial pressure coupled to the internal noise in the SR behavior of the system, which shows that the various external noise sources have different effects in the SRIN. And different roles of positive or negative feedback of the external noise terms may be a probable mechanism for the difference.