The invention relates to a method of extracting crystalline carbon from a metal smelting waste and an electronic waste combustion waste. The method comprises the following steps of: firstly, removing part of impurities in the metal smelting waste or the electronic waste combustion waste by an ascending pulse pneumatic process; then enriching crystalline carbon by means of a liquid flotation method; removing magnetic substances by means of a magnetic process; and finally, purifying the crystalline carbon by an acidic method to obtain a crystalline carbon product, the carbon content of which is greater than or equal to 99%.