Abstract: Objective To study construction and expression of mouse cdc25B protein.Methods The Cdc25B gene was amplified by PCR,enzyme digest and linked behind PG EX4T-2.After inducing with I PT G,the targ et gene was primarily expressed.Results T he Cdc25B gene consisted of about 900bp by DN A electrophoresis.The prokaryotic expression vector of PGEX4T-2/Cdc25B was constructed.After induction,a new anticipated Mr 53K D band appear ed in Westen-Blot.Conclusion Fusion proteins of GST/Cdc25B are successfully expressed in BL 21.This study is a basis for the role of Cdc25B during mouse oocyte maturatin.