The invention relates to a process for preparing a magnetic composite to be used as a magnetic carrier of active substances and as a therapy instrument for targeted delivery and controlled release of medicaments. According to the invention, the process consists in the synthesis of a polymer matrix using 3,9-divinyl-2,4,8,10-tetraoxyspiro[5,5]undecane and maleic anhydride, in a molar ratio of 1:2, in a 22.5% dioxane solution, in the presence of a radical initiator, functionalization thereof by cleaving the maleic cycle within the maleic anhydride, using the reaction with erythritol and preparation of the claimed magnetic composite with magnetite addition, as dispersion or powder, in situ.
