Deep freezing is a common treatment measure adopted by archives to prevent biological hazards. In this paper, the black suspected mildew spots on an archive that has been frozen at low temperature were sampled, and the samples were identified by morphological observation, ITS and 18S. It was found that there were still mildew that could be cultured. From the perspective of growth characteristics and metabolites, these molds are harmful to the archive carrier, and effective control measures should be taken urgently. Alcohol erasure of mildew is a common method in the repair process. We observed the state of mildew on the surface of paper carrier and the formation process of mildew through the simulation experiment of paper mildew under high humidity environment, and then used 75% alcohol erasure to observe the residue of mildew mycelia in the paper fiber. Based on the experimental results and the analysis of the temperature and humidity trend in an archives for three consecutive years, some suggestions were put forward for the inspection and restoration of moldy archives.