The utility model relates to a day-and-night spectrum reflection type oil-bleaching filed monitoring device, which comprises a spectrometer with a data collector which is arranged on a holdfast and a standard reflection plate which is fixed on a movable supporting board of the holdfast, which is characterized in that the device further comprises a light source for lighting a measuring face which is arranged on the upper portion of the spectrometer. The light source is a daylight-imitating light source which approximates to the solar spectrum in the spectrum range of 450nm-900nm. The utility model adopts natural lights or common lamp lights as light source, avoids large power and expansive light source, omits the complicated processes such as emulation or sampling for polluted oil, realizes the non contact type in-site measurement, and makes the measurement more economical, faster and simpler. The spectrum reflection method is adopted to monitor whether oil-bleaching exists or what kinds is the oil-leaching, and further can play a certain monitoring role for seaweed and red tide of sea water.