Abstract: The present application relates to the field of biotechnology, particularly to a plasmid target, a primer probe, a kit and a method for detecting residual host DNA in a cellular or viral formulation. The plasmid target is one or two selected from a plasmid Ori and a KanR gene, the Ori element has a gene sequence of SEQ ID NO. 1, and the KanR gene has a gene sequence capable of encoding a Kan R peptide chain, wherein the Kan R has amino acid sequences of SEQ ID NOs. 2-5. The present application also relates to a primer probe for the plasmid target, a kit, and a applying method.