The invention relates to a water-soluble florfenicol powder and its preparation method and application. According to parts by weight, it consists of 10 parts of florfenicol powder, 3-5 parts of citric acid, and 2-3 parts of polyvinylpyrrolidone PVPK30, 50-60 parts of lactose, 2-4 parts of sodium lauryl sulfate, 5-7 parts of polyethylene glycol 6000, 2-3 parts of trimethoprim lactate, 2-4 parts of palm oil. The present invention uses polyethylene glycol 6000, citric acid, polyvinylpyrrolidone PVPK30, lactose, sodium lauryl sulfate, palm oil, and various components to synergistically improve the water solubility of florfenicol and trimethoprim lactate, to maximize its efficacy.