The present invention provides a pyrolysis tube for enhancing the yield of olefins and reducing a coking tendency in steam cracking of hydrocarbons. According to the present invention, the pyrolysis tube is characterized in that a plurality of mixing blades made by twisting two ends of a plate in opposite directions are included therein. The yield of ethylene is thereby improved and the coking tendency is reduced by mixing a fluid flow, improving a heat transfer rate and shortening a residence time of the reactants therein.