The invention discloses powder for treating beriberi and a preparation method thereof. The powder comprises the following components: pericarpium arecae, cortex acanthopanacis, pawpaw, rhizoma nardostachyos, radix stephaniae tetrandrae, fructus evodiae, rhizoma atractylodis, phaseolus calcaratus, bunge cherry seed, dolichos lablab, fenugreek, betel nut and coix seed. The preparation method comprises the following steps: (1) drying pericarpium arecae, cortex acanthopanacis, pawpaw, rhizoma nardostachyos, radix stephaniae tetrandrae, fructus evodiae, rhizoma atractylodis, phaseolus calcaratus, bunge cherry seed, dolichos lablab, fenugreek, betel nut and coix seed for later use; (2) sterilizing pericarpium arecae, cortex acanthopanacis, pawpaw, rhizoma nardostachyos, radix stephaniae tetrandrae, fructus evodiae, rhizoma atractylodis, phaseolus calcaratus, bunge cherry seed, dolichos lablab, fenugreek, betel nut and coix seed dried in the step (1) through ultraviolet rays; and (3) sufficiently stirring and mixing the raw materials sterilized in the step (2), grinding the materials into powder through a grinder, sieving, collecting powder, sealing and packaging depending on dosage. The powder disclosed by the invention not only has functions of clearing heat, promoting uresis, detoxifying and killing insects, but also can kill fungi effectively and cure beriberi; and the powder is gentle in efficacy and causes no injury to foot skin.