A lignin-based copolymer with good biocompability was successfully prepared via atom transfer radical polymerization (ATRP) for efficient gene delivery. Kraft lignin was modified into lignin-based macroinitiators and then poly(glycidyl methacrylate)-co-poly(ethylene glycol)methacrylate (PGMA-PEGMA) side chains were prepared via ATRP grafting onto lignin. Ethanolamine was sequentially functionalized onto lignin-PGMA-PEGMA and a cationic lignin-PGEA-PEGMA copolymer consisting of a lignin core and different-length PGEA-PEGMA side chains was produced. Lignin-PGEA-PEGMA copolymers could efficiently compact pDNA into nanoparticles with sizes ranging from 150 to 250 nm at N/P ratios of 10 or higher. The gene transfection efficiency depends greatly on the mass percentage of PGEA units and the N/P ratio. The lignin-PGEA-PEGMA with 46.9% (mass%) of PGEA units (i.e. LG100) has highest transfection efficiency in comparison with the copolymers with a lower amount of PGEA units. In addition, LG100 has high transfection efficiency under serum conditions, which is comparable to or much higher than PEI control in HEK 293T and Hep G2 cell lines. More importantly, lignin-PGEA-PEGMA copolymers have excellent antioxidant activity. The novel cationic lignin-PGEA-PEGMA copolymers can be promising gene carriers for gene delivery.