5' terminal regulatory region of ovalbumin gene, a 1.2 kb DNA segment, was amplified by PCR from oviduct genome of a laying duck. It was cloned into the multiple cloning site of phD18-T vector (now named pOV), and used as regulatory sequence for promoting exogenous gene expression after enzyme cutting and sequencing identification. It was therefore preparation for constructing an expression plasmid vector to express exogenous genes.