The Ga+ focused ion beam (FIB) etching characteristics of TiNi thin films have been investigated. The thin films were deposited on Si(1 0 0) substrates by co-sputtering TiNi and Ti target using magnetron-sputtering system. Optical Microscope and atomic force microscopy (AFM) was used to analyze the etching rate and surface morphology of the TiNi. Experimental results show that the etched depth depends linearly on the ion fluence per area with a slope of 0.28 μm3/nC. But the etching rate decreases with increasing the ion beam current. The surface became smoother after FIB milling. The root-mean-square (rms) surface roughness changes nonlinearly with ion fluence with a minimum rms of about 4.3 nm at a fluence of about 3.1×1017 ions/cm2. The rms surface roughness decreases with increasing the ion beam current and reaches about 3.3 nm as the ion beam current is increased to 2 nA. A periodical ripple topography was observed.