The present invention relates to a lobaplatin crystal and a preparation method and drug application thereof, the lobaplatin crystal form is B, the melting point Tm. p. . is 230 +/-5 DEG C, diffraction peaks exist at the 2 theta angle values of 8.25, 9.77, 11.70, 13.13, 15.28, 16.48, 17.22, 17. 74, 19.01, 19.56, 22.28, 23.72, 24.04, 24.30, 25.62, 26.20, 28.57, 30.22 and 30.61 in an X-ray powder diffraction PXRD spectrum, wherein the 2 theta angle value error is in the range of 0.2. The crystal form B is obtained by solvent evaporation of lobaplatin trihydrate, or volatilization at room temperature after addition of a solvent in lobaplatin dihydrate or solvent-out crystallization, and drying. Compared with lobaplatin and the lobaplatin trihydrate in the prior art, the lobaplatin crystal in the crystal form B has better stability and solubility, is more suitable for the preparation of various forms of pharmaceutical preparations and storage and use, and can be better used to treat cancers such as breast cancer, small cell lung cancer or chronic granulocytic leukemia.