Garnet is one of the main indicator minerals of kimberlite type diamond deposits in Mengyin, Shandong Province. In order to determine the types of complex color garnets in diamond deposits of Mengyin and the relations between characteristics of garnet and ore potential, the research group systematically sampled the garnets in kimberlite of different mineralization degrees in ore deposits. The MgO, SiO₂, FeO, TiO₂, Al₂O₃, Cr₂O₃, CaO, MnO values of 50 single crystal garnets in the kimberlite were measured by electron microprobe spectrometer. 128 garnet single crystal lattice parameters were measured by X-ray single crystal diffraction. Some data were obtained: In the garnet, MgO values vary in the range of 14.44%～23.44%, SiO₂ 40.34%～43.64%, FeO 5.87%～16.97%, TiO₂ 0.00%～1.45%, Al₂O₃ 14.25%～22.30%, Cr₂O₃ 0.00%～11.88%, CaO 2.88%～6.68%, CaO/MgO ratios are in the range of 0.12 ～ 0.44, FeO/MgO 0.25～1.15, Cr₂O₃/Al₂O₃ 0.00 ～ 0.61, and TiO₂/Al₂O₃ 0.00～0.07. According to the above data, the garnets in kimberlite of Mengyin are probably of the magnesium, iron and calcium- aluminum chromium garnet series. In order to divide types of the garnets in kimberlite, the authors calculated the formula of the 50 garnets according to the chemical composition, and the results show that the chemical formula of garnet group minerals in kimberlite is A₃B_{2 3}. Group A cations are composed of Mg²⁺, Ca²⁺ and Fe²⁺. Divalent cation is mainly Mg²⁺. Mg²⁺ occupies about 53%～82% of the dodecahedron cavity center. Ca²⁺ occupies less than 7%～17% of the dodecahedral cavity center. Fe²⁺ occupies around 5%～31% of the dodecahedron cavity center. Group B cations are composed of Al³⁺, Cr³⁺ and Fe³⁺. Trivalent cation is mainly Al³⁺, with [AlO₆] octahedra occupying up to some 62%～92%, and [FeO₆] and [CrO₆] octahedra occupying less than 38%. According to different cations that occupy dodecahedral cavities and octahedral cavities, garnets in Mengyin can be divided into 10 subspecies. According to Dawson-Stephens garnet classification methods, garnets in kimberlite of Mengyin are mainly of G9 and G10. The content of Cr₂O₃ in G9 garnets is low, the content of CaO is high, and iron chromium garnet end-member is characterized by a high percentage of molecules, with the color being mainly of purple series. G10 garnets are mainly in the coarse-grained kimberlite diamond, with a large number of diamond inclusion garnets belonging to this class, which reflects the genetic relation of coarse-grained garnet with diamond. G10 garnet may indicate the existence of diamond-bearing kimberlite body. According to the composition of garnets in kimberlite of Mengyin, the garnet of kimberlite in diamond of this area had formation pressure of 6.0～9.0 GPa. It is inferred that garnet in kimberlite of Mengyin should belong to asthenosphere. Lattice parameter statistics of 128 garnets show that lattice parameters of garnets from Mengyin are distributed in the range of 1.151～1.161 nm, with the frequency distribution in the range of 1.154～1.160 nm. Purple garnet lattice parameters indicating no ore, lean ore, medium ore-bearing rock and rich ore rock are 1.162 nm, 1.159～1.160 nm, 1.156～1.160 nm and 1.155～1.157 nm respectively. From barren rock through lean ore rock, medium ore-bearing rock, to rich ore rock, purple garnet lattice parameter values tend to decrease. Purple garnet cell parameters thus have obvious prospecting implications for kimberlite in Mengyin of Shandong Province.