Oncogenic microRNAs are essential components in regulating the gene expression of cancer cells. Especially miR21， which is a major player involved of tumor initiation， progression， invasion and metastasis in several cancers. The delivery of anti-miR21 sequences has significant potential for cancer treatment. Nevertheless， since anti-miR21 sequences are extremely unstable and they need to obtain certain concentration to function， it is intensely difficult to build an effective delivery system for them. The purpose of this work is to construct a self-assembled glutathione (GSH)-responsive system with tumor accumulation capacity for effective anti-miR21 delivery and cancer therapy. A novel drug delivery nanosphere carrying millions of anti-miR21 sequences was developed through the rolling circle transcription (RCT) method. GSH-responsive cationic polymer polyethyleneimine (pOEI) was synthesized to protect the nanosphere from degradation by Dicer or other RNase in normal cells and optimize the pompon-like nanoparticle to suitable size. Dehydroascorbic acid (DHA)， a targeting molecule， which is a substrate of glucose transporter 1 (GLUT 1) and highly expressed on malignant tumor cells， was connected to pOEI through PEG， and then the polymer was used for contracting a RNA nanospheres into nanopompons. The anti-miR21 nanopompons showed its potential for effective cancer therapy.