The invention relates to a quaternary aromatic acid binuclear zinc complex serving as mercury ion fluorescent probe and a preparation method of the complex. the chemical formula of the complex is [Zn2(bptc)4.(bpy)2.H2O], wherein bptc is 3,3',4,4'-four carboxyl benzophenone, and bpy is 4,4'-bipyridyl; the complex adopts a three-dimensional nanometer-sized micropore structure. When the complex serves as the mercury ion fluorescent probe, mercury ion can not influence the position of a fluorescent emission peak of the quaternary aromatic acid binuclear zinc complex, and the intensity of the emission peak of the complex is enhanced remarkably as the concentration of Hg2+ ion increases (the maximum enhanced extent can reach about 45 times). The complex can serve as a fluorescent probe of Hg2+ ion and has a potential application prospect in the field of environmental monitoring and life science.