Abstract: To establish a rapid method for determination of mercury in grain, Rhodamine type B fluorescent probe was synthesized and used as the carrier and chromogenic group of the probe system. The original fluorescent probe system was made into a visible light probe system, where this principle was used in conjunction with extraction assisted by effervescent tablets to establish a rapid method for the detection of elemental mercury (Hg) in grain. The initial speed of the blast reaction was controlled via the use of the bubble tablet blast method and the loss of Hg could be reduced in the course of the initial blast. After combining with different concentrations of Hg, the probe system make the originally colorless probe system turn into a rosy red color. The color developing probe system was in the range of 0.5~20 ng/g of Hg content in the sample at 550 nm, and the shade of color was proportional to the Hg content, whose range in the samples could also be assessed using a colorimetric card with naked eye. In the present study, the recoveries were 90.98%~102.46%, the precision RSD was 2.76%~4.76% and the detection limit was 1.0 ng/g. The rapid detection method has the advantages of high efficiency, accuracy, high sensitivity, specificity and wide applicability. Taken together, it is suitable for bulk screening and detection of elemental mercury in grains, wheat and other grains and their food products. Also, the method and principle might provide novel insights for the field of visualization probe rapid detection.