Optical logics can be achieved by utilizing four-wave-mixing (FWM) effects in micro-nano waveguides. We analyze the contributions of signal noise onto the efficiency of FWM in such nonlinear waveguides. Since Gaussian noise exists extensively in most practical systems, we analyze the FWM process of the input signals, which are affected by amplitude noise, frequency noise, phase noise and additive noise in the metal-insulator-metal (MIM) waveguides. Results show that, with the average power of the phase noise increasing over 1.44, the normalization intensity of the idle light generated in the FWM process is less than -40 dB, compared to -18 dB without noise, indicating a significantly reduction of nonlinear efficiency. However, if the signals are affected by other kinds of noise, the intensity of the idle light is nearly the same as that without noise. Therefore, FWM process in such waveguides is sensitive to Gaussian phase noise, while it′s not sensitive to other kinds of noise.