Based on the relative free energy and Youngs equation,the wetting mechanism of the unidirectional groove array structure on the surface of Ni-Ti alloy was explored from the parallel groove direction and the vertical groove direction.The contact angle models under Wenzel state and Cassie-Baxter state were established,and the theoretical values of contact angle under different size parameters were analyzed.The surface of Ni-Ti alloy was modified by micro-milling technology to process the required microstructure.The surface morphology,size parameters and actual contact angle were measured and analyzed by the VHX5000 super depth 3D microscope and JC2000D1 contact angle measuring instrument.The results show that the Ni-Ti alloy surface array structure prepared by micro- milling has good dimensional accuracy and complete structural boundary,which meets the design requirements;the actual contact angle in parallel direction decreases with the increase of column width,and the maximum static contact angle is 145.4°,which is consistent with the trend of Cassie-Baxter contact angle in parallel direction;the theoretical contact angle of the Cassie-Baxter state in the vertical direction is numerically equal to the intrinsic contact angle of the Ni-Ti alloy surface;at the same time,the actual contact angle in the vertical direction is inconsistent with the Wenzel state contact angle,and the error is within 42.1°.