[Objective]To investigate the influence of Nitinol modified on its surfaces by the coating of titanium or titanium-niobium alloy on separat ion of Ni~(2+).[Method]The specimens from 1 to 7 days after the experiments were collected and the concentration of Ni~(2+) were cletermined by physiologic saline immersing test,low temperature ashing furnace,Mg(NO_3)_2 as matrix modifier and graphite furnace atomic absorption spectrometry(GFAAS).[Result]Specimens of Nitinol were devided into 3 groups:alloy coated with Ti(Ti group);alloy with Titanium-Niobium(TiNi group);only Nitanol without coating group.Obvious separation of Ni~(2+) was detected in the groups of Nitinol that were not modified and were put in baking oven(37℃),the separating procedure was mainly within 4 days,the separation rate(10~(-7)??g? cm~(-2)?s~(-1)) from the first to the forth days was 18.2,3.45,1.75 and 0.45 respectively,the Ni~(2+)was no more separated from the fifth day.Whereas,Ni~(2+) was not separated in the groups of Nitinol that were modified by the coating of metallic Ti and TiNb alloy.The recovery rate of the experiments was between 94.6%～108.6%.[Conclusion]The coating of Ti or TiNb on the surfaces of Nitinol stopped Nitinol from separating Ni~(2+).