Gene vectors with high biocompatibility and transfection efficiency are critical for successful gene therapy. PEI 25K (Polyethyleneimine 25K) is a common polymeric gene vector that has been employed as a positive control material in gene transfection studies due to its good performance in endosome escape. PEI 25K's indegradability and abundance of positive charges, on the other hand, cause toxicity in cells, limiting its use. In this study, we developed the PEI-ER non-viral vector by adding an endoplasmic reticulum (ER) targeting ligand to low molecular weight PEI 1.8K. These small molecule modifications dramatically improved PEI transfection efficiency while barely interfering with compatibility. PEI-ER/DNA complexes were discovered to enter the cell via caveolin-mediated endocytosis, avoiding destruction in the endosome. We believe that this little chemical alteration is a simple solution to enhance the efficacy of cationic polymer vectors in gene transport, and it has a lot of medicinal applications.