A water-stable two-dimensional lanthanide organic framework, {Eu(BTB)DMF} (Eu-(BTB)DMF}(n) = N,N-dimethylformamide), with two one-dimensional channels was obtained, and its structure was characterized. With changes in the amount of LiOH"H2O, different sizes of {Eu(BTB)DMF}n were synthesized. The prepared EuMOF powder is easy to disperse in water and exhibits typical Eu red emission. The fluorescence properties showed that Eu-MOF can detect sulfamethzine (SMZ) with high sensitivity and selectivity. Finally, the as-synthesized Eu-MOF was successfully used for the detection of SMZ in surface water by a standard addition method.