The present invention provides a hydrobromide of methyl 3-[(4s)-8-bromo-1-methyl-6-(2-pyridyl)-4H-imidazol[1,2-a][1,4]benzodiazepine-4-yl] propionate and its related crystal forms, preparation method and use thereof. The hydrobromide has excellent solubility (>；100 mg/ml), which is significantly superior to other currently commercially available or developed salt products, and is especially suitable for the preparation of injections, has relatively good stability in various crystal forms, and has good practical value and market prospects.
