The invention relates to a novel crystal form (beta) of clindamycin phosphate, and a preparation method. In an XRD powder diffraction pattern irradiated by Cu-K[alpha], characteristic peaks appear at 2[theta] angles of 5.7+/-0.1 degrees, 11.5+/-0.1 degrees, 15.5+/-0.1 degrees, 17.9+/-0.1 degrees, 21.7+/-0.1 degrees and 24.6+/-0.1 degrees. The novel crystal form (beta) of clindamycin phosphate is obtained by dissolving crude clindamycin phosphate in a mixed solvent of deionized water and a low alcohol, wherein an initial mass concentration of the crude clindamycin phosphate is 0.12-0.15 g/mL; heating the solution with stirring until the clindamycin phosphate is dissolved and the solution is clear; thermal filtering; cooling for crystallization; filtering the crystal; and drying at the temperature of 60-70 DEG C. The crystal has good stability; the crystal remains white powder after being placed 10 days at the high temperature of 60 DEG C; and the X-ray diffraction pattern has no obvious change.