A rare earth complex Eu(MAA)3Phen was prepared with methacrylic acid and o-phenanthrolineas ligands under mild conditions. The complex has a fluorescence emission centered at 618 nm with a half-peak width of 15 nm. Since the emission peak of the complex matches the absorption peak of malachite green (MG), the fluorescence of the complex will be quenched by MG through the fluorescence resonance energy transfer effect. The fluorescence testing conditions for MG were optimized based on fluorescence intensity and fluorescence quenching efficiency. The FRET efficiency was calculated to be 0.21. Under the optimal conditions, the response time was only 5 min. Compared with sulfonamides, chloramphenicol and other banned fishery drugs, the complex exhibited the highest quenching efficiency to MG. The linear range was 0.5–20 μmol L-1, and the detection limit was 117.29 μmol L-1(3σ/S, n = 9).This complex was used to detect MG residue in aquaculture water, and the recoveries were between96.10% and 98.76%, indicating that the prepared fluorescent probe could be used for the rapid detection ofMG in aquaculture water.