The invention discloses a preparation method of molybdenum powder, comprising the following steps of: firstly, sieving the raw material of molybdenum trioxide to obtain molybdenum trioxide powder; secondly, carrying out primary reductive reaction on the molybdenum trioxide powder and hydrogen gas in a primary reduction furnace to generate molybdenum dioxide; thirdly, carrying out secondary reductive reaction on molybdenum dioxide and hydrogen gas in a secondary reduction furnace to generate rough molybdenum powder; and fourthly, sieving the rough molybdenum powder and mixing to obtain the finished molybdenum powder. The preparation method provided by the invention is easy to control, simple and convenient to operate, safe and reliable and suitable for industrial mass production. A molybdenum block pressed by using the molybdenum powder prepared by using the preparation method provided by the invention is high in flexural strength, and the prepared molybdenum and copper alloy is high in yield, good in material consistency, long in service life and capable of being used as a braking/heat radiating material.