In this study, we report that HBV promotes abnormal tumour blood vessel formation in HCC through the BMP9/Rho/ROCK/myosin light chain (MLC) axis and describe a potential application of UTMD‐mediated BMP9 delivery as a strategy that might enhance the cytotoxicity of clinical immunotherapy toward HBV‐associated HCC. The gene discussed is MLC1; the disease is neoplasm.