The invention provides an aqueous fluorescent tracer and a preparation method thereof. The aqueous fluorescent tracer has a chemical structure shown in the description; and R in the chemical structureis -SO3Na, -(CH2)2NH(CH2)2SO3Na, -Ph-SO3Na, -Ph-COOC2H2SO3H or a group with the formula being shown in the description. The preparation method of the aqueous tracer comprises the following steps: carrying out a condensation reaction on salicylaldehyde and diethyl malonate with piperidine as a catalyst to obtain a first product; carrying out a hydrolysis reaction on the first product under an alkaline condition to obtain a second product; and reacting the second product with aminosulfonate to prepare the aqueous fluorescent tracer. The aqueous fluorescent tracer has the advantages of good water solubility, low cost, non-toxicity, good chemical and biological stability, good thermal stability, simplicity in analysis operation, small dosage, high sensitivity, and convenience in monitoring.