Molecular magnetic refrigerating material is a kind of green and environmentally friendly materials, which achieve the purpose of cooling by its magnetocaloric effect. Magnetic density is crucial to the magnetocaloric effect of the complexes, and it is usually described by the parameters of Mw/NGd or metal/ligand mass ratio, which represents the content of Gd (III) in the complexes. In order to establish the functional relation between these parameters and magnetocaloric effect, doping is a credible method without changing the coordination environment of the system, which is realized by the process of increasing Gd (III) gradually in the diamagnetic complex. Hence, a diamagnetic dinuclear Y2, four doped samples Gd0.24Y1.76, Gd0.51Y1.49, Gd1.04Y0.96, and Gd1.46Y0.54, and a pure dinuclear Gd2 were synthesized and characterized. Through the measurement of magnetic properties and data fitting, the functional relations were obtained between these parameters and −ΔSm in this dinuclear system. It is the first time that the relationships are set up via experimental design, and it will contribute to observation and comprehension of how magnetic density affects the magnetocaloric effect. In addition, the −ΔSm of dinuclear Gd2 is 29.96 J kg−1 K−1, which is higher than most of the reported dinuclear Gd (III)‐based complexes.