The invention provides a method for detecting a fluorescent brightening agent in paper. The method comprises the steps as follows: 1), sample pretreatment: preparing a standard fragment sample, and soaking the standard fragment sample by different solutions respectively after weighed; 2), adjusting the excitation wavelength of a fluorospectro photometer to be 345 nm, and detecting the sample; 3), weighing a defined quantity of a VBL fluorescent brightening agent to configure a standard liquid with appropriate concentration, scanning an excitation curve and an emission curve, and measuring a standard curve; and 4), measuring the content of the fluorescent brightening agent in different paper samples, and obtaining the content of the fluorescent brightening agent of the detected paper sample through comparison with the standard curve. Compared with a traditional detecting method, the method provided by the invention can detect relevant data rapidly and accurately, the problem of manual interpretation errors caused by manual operation is avoided, and the health and safety of relevant toilet paper products can be elevated accurately; and meanwhile, experimental instruments adopted by the invention are simple, the data repeatability is good, the reliable quality monitoring guarantee is provided, and accordingly the guaranteeing advantages on the product quality monitoring are achieved.