The invention discloses a switch-type ferric ion fluorescence probe and a preparation method thereof. Rhodamine B is adopted as a matrix of the switch-type ferric ion fluorescence probe, and the structural formula of the switch-type ferric ion fluorescence probe is as follows (refer to the Specification). According to the invention, fluorescence probe molecules demonstrate higher selectivity and sensitivity in the concomitant system of ferric ions and other positive ions; a fluorescence development experiment shows that the fluorescence probe molecules have excellent cell penetrability, are nontoxic for cells, and can be used for detecting the concentration and distribution of ferric ions in cells.