In this work,Co epitaxial thin films with 2.5nm thickness were prepared on single-crystal MgO(001)substrates and annealed at different temperature(200℃,300℃,400℃,560℃).The structure was characterized through the LEED.The magnetic and transport property were investigated through MOKE and AMR.The results show that the LEED points are brighter and brighter as the increasing of the annealing temperature,and the structure of the films in high annealing temperature(above 200℃)have better epitaxial growth.Comparing the magnetic properties of the as-deposited one with the annealed ones,we found that the magnetic anisotropy was affected by the annealing temperature deeply.The magnetic anisotropy of the as-deposited one shows superposition of a weakly four-fold and a powerful two-fold contribution due to strain from the interface which the easy axis is along the direction of one of the easy axis of four-fold symmetry.We found that magnetic anisotropy and uniaxial anisotropy in the MgO/Co/Cu film was significantly decreased due to decreased magnetoelastic anisotropy caused by stress built up most likely at the MgO/Co interface during annealing.When the films were annealed above 300℃,the films show isotropy however the LEED is very good.Meanwhile,the coercivity became larger and larger from 45Oe(room temperature)to 1200Oe(560℃)at the easy axis direction as the increasing of annealing temperature.Furthermore,the magnitudes of various magnetic anisotropy constants were derived from torque curves on the basis of AMR results.The results further prove the phenomenon shown in the MOKE.Our experimental results prove that the Co/MgO interface plays an essential role in inducing strong UMA in the films.The precise investigation of annealing effect on both UMA and four-fold anisotropies can provide a methodological solution to improve the coupling of the interface that can serve as the core unit of spintronic devices.