Rationale:CRISPR-Cas13a is an efficient tool for robust RNA knockdown with lower off-target effect, which may be a potentially powerful and safe tool for cancer gene therapy. However, therapeutic effect of current cancer gene therapy that targeting monogene was compromised by the multi-mutational signal pathway alterations of tumorigenesis.Methods:Here, hierarchically tumor-activatednanoCRISPR-Cas13a (CHAIN) is fabricated for multi-pathway-mediated tumor suppression by efficient microRNA disruptionin vivo. A fluorinated polyetherimide (PEI; Mw=1.8KD) with graft rate of 33% (PF33) was utilized to compact the CRISPR-Cas13a megaplasmid targeting microRNA-21 (miR-21) (pCas13a-crRNA) via self-assemble to constitute a nanoscale 'core' (PF33/pCas13a-crRNA), which was further wrapped by modified hyaluronan (HA) derivatives (galactopyranoside-PEG2000-HA, GPH) to form CHAIN.Results:The dual-tumor-targeting and tumor-activated CHAIN not only manifested long-term circulation, but augmented tumor cellular uptake and endo/lysosomal escape, thus achieving efficient transfection of CRISPR-Cas13a megaplasmid (~ 13 kb) in tumor cells with minimal toxity. Efficient knockdown of miR-21 by CHAIN restored programmed cell death protein 4 (PDCD4) and reversion‐inducing‐cysteine‐rich protein with Kazal motifs (RECK) and further crippled downstream matrix metalloproteinases-2 (MMP-2), which undermined cancer proliferation, migration and invasion. Meanwhile, the miR-21-PDCD4-AP-1 positive feedback loop further functioned as an enhanced force for anti-tumor activity.Conclusion:Treatment with CHAIN in hepatocellular carcinoma mouse model achieved significant inhibition of miR-21 expression and rescued multi-pathway, which triggered substantial tumor growth suppression. By efficient CRISPR-Cas13a induced interference of one oncogenic microRNA, the CHAIN platform exerted promising capabilities in cancer treatment.