In current study, a ratiometric fluorescence sensor (FSS@MOF-5/GMP-Eu) based on self-assembly of Eu and guanosine monophosphate (GMP) on the surface of fluorescein loaded MOF-5 (FSS@MOF-5) is designed and fabricated for visual detection of tetracycline (TC). As the TC recognizer, Eu specifically reacts with TC to form EuTC complex and results in fluorescence enhancement due to the antenna effect. With the TC addition, visible fluorescence changes from yellowish-green to orange and finally to red can be easily observed by naked eyes. The proposed FSS@MOF-5/GMP-Eu displays an excellent linear relationship with TC (0–20 μM), providing a low detection limit of 18.5 nM. The ratiometric sensor exhibits excellent selectivity to TC against other interferents owing to the formation of EuTC complex. The prepared FSS@MOF-5/GMP-Eu can be employed for TC detection in milk and pork and will also be valuable for use in fluorescence sensor applications.