In this paper, we suggest a new physical mechanism for the in 1/f noise metals phenomena, which have a history of experimental observation for more than forty years. We propose that the 1/f noise is caused by the diffusion transportation with infrared divergence of the local electrons in metals. Based on the general theory of the low-frenquency fluctuation, dissipation and relaxation, a non-Markovian diffusion equation is established. The noise spectra deduced from this equation can explain the four basic characteristics of the 1/f noise. With reasonable choice of parameters, our noise spectra agree fairly well with experimental results. Some further discussions concerning the current theory and related problems are also given.