Abstract: The present invention relates to a benzoxazine based copolymer aerogel obtained by reacting a benzoxazine monomer or oligomer and a comonomer selected from the group consisting of an isocyanate compound, a cyclic ether compound and an acid anhydride compound in a presence of a catalyst and a solvent, wherein said catalyst is an optional ingredient when said comonomer is an acid anhydride compound or an isocyanate compound. Benzoxazine based copolymer aerogel according to the present invention provides high thermal insulation material, while good mechanical properties and performance is maintained.