The invention discloses an application of a five-replaced-ectoine-biosynthesis compound in measuring the surfactant critical micelle concentration with the titration method. The five-replaced-ectoine-biosynthesis compound with the structure shown in the formula defined in the description serves as a fluorescence indicator, and the five-replaced-ectoine-biosynthesis compound is prepared into a fluorescence indicator storing solution with a solvent; then a to-be-detected surfactant is prepared into a sample solution with the concentration higher than the critical micelle concentration; the two solutions are mixed and prepared into titrating solutions with the different concentrations and titrated solutions with the different concentrations, the titrated solutions are titrated with the titrating solutions, mutation of the fluorescence intensity from the fluorescence-free degree to the high fluorescence degree is observed under an ultraviolet lamp, and a mutation point is the surfactant critical micelle concentration. The structural formula of the ive-replaced-ectoine-biosynthesis compound is shown in the formula (I); the five-replaced-ectoine-biosynthesis compound is applied to the CMC value of a surfactant measured with the titration method, the operating method is sensitive, rapid, simple and good in application prospect. The formula is defined in the description.