The invention relates to a method for improving the function stability of a nickel-titanium shape memory alloy, and belongs to the field of nickel-titanium shape memory alloys. According to the method, dislocations and other defects are introduced into the nickel-titanium shape memory alloy, the dislocations serve as activity position points for promoting second phase nucleation, then, fine and evenly-distributed nano reinforcement phases are formed in a matrix structure of the nickel-titanium shape memory alloy through later aging treatment, accordingly, the matrix strength of the nickel-titanium shape memory alloy is obviously improved, and then the function stability of the alloy is improved. Meanwhile, in the method, only temperature martensite phase change induction circulation or stress martensite phase change induction circulation need to be conducted on a nickel-titanium shape memory alloy component before aging treatment, and operation is simple and convenient; and the methoddoes not have the requirement for the shape of the nickel-titanium shape memory alloy component, and the method is adaptive to the complex nickel-titanium shape memory alloy component and capable of effectively improving the function stability of the complex nickel-titanium shape memory alloy component.