The invention discloses a method for preparing carbon nanotubes from coal. The method comprises the steps that pulverized coal is mixed with water, melamine and a soluble cobalt salt or a nickel salt,then a high-energy ball mill is utilized for wet milling to obtain a slurry-like mixture, and after the mixture is subjected to freeze drying, a porous blocky material is obtained; the blocky material is placed in a high-temperature atmosphere furnace to be sintered in a hydrogen/argon mixed atmosphere, and thus the clustered carbon nanotubes can be prepared; and finally, the pure carbon nanotubes are obtained through pickling and washing with water. The natural coal is utilized as the raw material, the coal does not need to be pre-treated, selectivity to the coal type is low, the yield is high, the diameters of the prepared carbon nanotubes are 40 nm to 100 nm, and the diameters of the carbon tubes are evenly distributed; and the preparation process is simple, a technology is simplified,the equipment requirements are low, the cost is low, and industrial production is easy to realize. The carbon nanotubes have great market demands and broad application prospects in the fields of lithium-ion batteries, super capacitors, nano catalysis, biomedicine, environmental protection and the like.