Calcineurin B subunit (CNB), as a regulatory subunit of the calcineurin, is a member of EF-hand calcium-binding proteins.In this study, Molecular dynamics simulations were performed to simulate Calcium-induced conformational change of CNB.Simulations of the fully Ca2+-saturated state of CNB (Holo-CNB) and the Ca2+-free state (Apo-CNB) were performed in solution for 20ns starting from the X-ray crystal structure of Holo-CNB binding with Calcineurin A subunit (CNA).Based on the trajectories of MD, we found that there was no drastic change between Holo-CNB and Apo-CNB.The modest difference mainly exists in the interhelical angles of four EF-hand motifs and solvent accessible surface area of hydrophobic groove, whereas both Holo-CNB and Apo-CNB hold an integrated hydrophobic groove, which implies that CNB, regardless of binding with Ca2+ or not, has the potential to bind with CNA, although distinguished in the affinity.The data in experiments of assay of phosphatase activity, pull-down and circular dichroism support the result of MD simulation.