Abstract: By using the NCEP reanalysis data and NOAA daily out-going long-wave radiation (OLR) data, and the daily precipitation data in Fujian in 2010, this paper reveals the atmospheric low-frequency characteristics of the persistent heavy rain and atmospheric low-frequency precursor signals before the persistent heavy rain through the analysis of typical persistent heavy rain in Fujian Province during the pre-flood season from June 13th to the 27th in 2010. The study shows that: (1) The precipitation in pre-flood season in Fujian in 2010 has obvious characteristics of low-frequency variation, the significant cycle is about 30—45 days, showing an obvious wet and dry window that is drier and rainy periods alternating, up to 15 days of persistent heavy rains that occurred in the final wet window. (2) During the persistent heavy rain, the configuration and change of the low-frequency system in mid-high latitudes and low latitudes is very conducive to maintaining the long period of heavy rain. The low-frequency variation of the South Asia high, the subtropical high, the blocking high in Ural Mountains, the East Asian trough and moisture transport from the Bay of Bengal and the South China Sea created this heavy rainfall process with the duration and strength being rarely seen in history. (3) This persistent heavy rain accompanied by once obvious East Asia monsoon surge, the intensity of the precipitation is closely related to the intensity of the atmospheric low-frequency oscillation. The heavy precipitation often appears in the 30—60 days' intraseasonal oscillation (ISO) and 10—20 days' the quasi-biweekly oscillation (BWO) superimposed wet phase. (4) The low-frequency system has significant ongoing and periodic characteristics, timely monitoring and mastering the variation discipline of the atmospheric low-frequency precursory signals. The system has a very important significance for the extended-range forecast of the persistent heavy rain in the future.