The invention relates to a structure, a preparation / crystallization method and partial characters of a cantharidin derivative. The compound is of a colorless rod crystal in appearance, the melting point is 126.0-127.2 DEG C, the molecular formula is C20H21N3O6, the chemical name is 2,2'-(3-azapentane-1,5-diyl)bi(3a,4,7,7a-tetrahydro-4,7-epoxy-1,3-dihydro-isoindole-1,3-dione), and the structure formula is shown in the specification. The structure is of a triclinic system, the space group is P-1, a is equal to 8.765(3) angstroms, b is equal to 9.709(3) angstroms, c is equal to 11.940(4) angstroms, alpha is equal to 76.723(4) degrees, beta is equal to 78.423(4) degrees, gamma is equal to 74.682(4) degrees, V is equal to 943.1(5) cubic angstroms, and Z is equal to 2. The preparation method of the compound is simple, and the compound has a mild inhibition effect on lung carcinoma cells and breast cancer cells.