Trace quantities of formaldehyde (FA) in water and food will cause great harm to the human body, and has received much attention in recent years. In this work, a luminescent metal organic framework (Eu³⁺@Bio-MOF-1) was successfully constructed to detect FA in water and food. Experiments show that the two luminescent centers of Eu³⁺@Bio-MOF-1 have completely different responses to FA and the two luminescent centers can offer a reference for each other, so it can be designed as a precise self-calibrating luminescent detector for FA. Based on this, a portable self-calibrating luminescent logic detector capable of gradient detection of FA is designed. The three different outputs of this logic detector are L (low), H (high), and VH (very high), corresponding to three different inputs (<6 ppm, 6–10 ppm, and >10 ppm). More importantly, the color differences can be easily distinguished by the naked eye under UV light, which makes a significant contribution to detect the concentration of FA more intuitively in our daily life.