The invention relates to an iron catalysis AGET (atom transfer radical polymerization) ATRP (atom transfer radical polymerization) system without a ligand in a biomass based solvent and a polymerization method. The AGET ATRP system comprises a polymerization monomer, an initiator, a high-valence iron halogen catalyst, a reducer and a biomass based solvent, wherein the biomass based solvent is ethyl lactate or r-valerolactone. The system takes the biomass based solvent as a green solvent and high-valence iron halogen as a catalyst; atom transfer radical polymerization is performed without the additional ligand; and a polymerization process comprises the following steps of: preparing a polymerization reaction system from the monomer, the initiator, the catalyst, the reducer and the solvent according to a certain mole ratio, and performing ATRP under an anaerobic or aerobic condition. A polymer prepared by the system is controllable in molecular weight and low in dispersity; the green biomass based solvent is applied in the polymerization process; the ligand is not required to be added; components of a polymerization reaction substance are reduced; environmental influence is reduced;and a green and low-cost living polymerization technology is provided.