The present invention relates to an eco-friendly lightweight aggregate with low carbon using a dry bottom ash by crushing and gravity grinding, and a manufacturing method thereof. More particularly, the eco-friendly lightweight aggregate of the present invention has an excellent aspect ratio of 1 to 2 range by crushing and gravity grinding the bottom ash discharged by air-cooling the same in a heat power plant, satisfies unit volume mass not more than 880 kg/m^3 (coarse aggregate) and not more than 1, 120 kg/m^3 (fine aggregate) which are a reference of structural KS lightweight aggregate, has absolute density of 1.3 to 1.8 kg/m^3 and total porosity of 26 to 50 w% which are an equivalent level comparing with an artificial lightweight aggregate circulated in the domestic and foreign countries, has high closed porosity of 13 to 46 w% and low absorptivity of 4 to 10%, which are outstanding levels compared to the artificial lightweight aggregate, and also has rough texture since a small spherical air gap is formed on a surface while a general shape is closer to a spherical shape.COPYRIGHT KIPO 2015