The invention relates to a 3-oxooleanolic acid monocrystal and a culture method thereof. The X-ray powder diffraction of the 3-oxooleanolic acid monocrystal has a characteristic peak at the following diffraction angles 2 theta: 5.120, 10.200, 15.320, 20.500 and 28.640; the 3-oxooleanolic acid monocrystal belongs to a monoclinic system, the space group is C2, the molecular number in unit cell Z=4;and the 3-oxooleanolic acid monocrystal is a white acicular crystal at normal temperature. The 3-oxooleanolic acid monocrystal is cultured by the following steps: recrystallizing a crush 3-oxooleanolic acid monocrystal product, and slowly volatilizing the solvent. The 3-oxooleanolic acid monocrystal provided by the invention has the advantages of high purity; and the culture method is simple to operate, and has the advantages of short time consumption, low requirements for purity of crude product, and simple technique.