Due to its excellent biofunctionality from shape memory effect and psuedoelasticity of the TiNi alloy, TiNi alloy is a promising candidate in the medical applications. The biocompatibility of a metal implant is generally evaluated by the reaction (or damage) of the surrounding tissue. The intensity of damage caused by metallosis is proportional to the quantity of (toxic) metallic ions produced by corrosion. The corrosion resistance of TiNi shape memory alloy can be substantially improved by the DC plasma-polymerized hexamethyldisilazane coating. From the results of IR spectrum, water contact angle measurements and SEM as well as AFM observations, higher monomer pressure will not accelerate the deposition, but also lead to the formation of the coatings with a smoother surface and a more organic nature. The immersion test of specimen in 37degreesC Ringer's solution indicates the coating will deteriorate from the analysis of electrochemical impedance spectroscopy (EIS). From the capacitance increment and the resistance decrement of coatings, the deterioration of coatings can be attributed to the water uptake during immersion.