Intracellular antibody refers to the recombinant antibody expressed intracellularly.Single-chain Fv fragment,one common form of intracellular antibody with high affinity,can be expressed in transfected nonlymphocytes and targets to a particular cellular compartment to interfere the activity of some macromolecular substances or the process of their secretion.Intracellular antibody has been proved to be capable of inhibiting growth factor receptors,inactivating oncoproteins and inhibiting HIV-1 replication. Intracellular antibody technique is a novel gene therapy approach with potentiality in medical application.