Abstract: A ductile shear zone has been found for the first time in the Cretaceous Yinggeling red basin,Hainan Island.It consists of mylonites and have well-developed lineation,foliation and fold structure,as well as the kinematic characteristics of detachment.The differential stress for deformation ranges from 27.2 to 66.2 MPa and the deformation temperatures are >500℃.Subvertical compression and subhorizontal extension suggest that the formation of the shear zone is related to intrusion of deep-seated magma.This has great geological significance for a further understanding of the Yanshanian tectonomagmatism and magmatic emplacement mechanism on Hainan Island.