The invention belongs to the field of water treatment chemicals and in particular relates to a composite non-phosphorus scale inhibitor which consists of a dendritic polymer, polyepoxy sodium succinate, sodium polyaspartate, IA-AMPS (Itaconic Acid-2-Acrylamide Amino-2-Propanesulfonic Acid) and water, wherein the dendritic polymer is a polyamide-amine dendritic polymer EDA-PAMAM (Ethylenediamine-Polyamidoaminedendrimer) with ethylenediamine as a core and amino as an end group; IA-AMPS is a copolymer of itaconic acid and 2-acrylamide amino-2-propanesulfonic acid as monomers through free radicalpolymerization reactions. The composite non-phosphorus scale inhibitor is free of phosphorus, the components have synergistic effects, mutual coagulation and polymerization of SiO2-PAMAM are prevented, coagulate precipitate can be reduced, the scale inhibition performance is greatly improved, and excellent scale inhibition performance can be achieved for CaCO3, CaSO4 and CaSiO3.