Diamond-like carbon (DLC) coatings with the thickness between 253-1880 nm were prepared on NiTi alloy by arc enhanced magnetron sputtering (AEMS). Surface profilometry, scratch tests, tribometry, and electrochemical tests were conducted to determine the mechanical properties and the corrosion behavior of the DLC-coated NiTi alloy, and it is found that DLC coatings with thickness between 700 and 1000 nm have moderate residual stress, high critical load, long wear life and good corrosion resistance. So DLC coatings with thickness between 700 and 1000 nm are suitable for improving the mechanical properties and corrosion resistance of biomedical NiTi alloy. The associated mechanisms were also discussed in detail.