Size control of Au-Ni heteronanostructure in synthesis was systematically studied in this paper. Monodispersed Au-Ni spindly nanostructures were obtained through noble-metal-induced-reduction (NMIR) strategy. In a typical synthesis, 0.05 g of HAuCl₄ and 0.25 g of Ni(NO₃)₂•6H₂O were added into 10 mL of octadecylamine (ODA) at 120 ℃. Then, the system was heated to 240 ℃; under this temperature, products were synthesized after 10 min of magnetic stirring. The products were collected by centrifugation and purified by washing with ethanol for several times. Transmission electron microscopy (TEM) and UV-Visible spectroscopy (UV-vis) were applied to characterize the morphology and size of the as obtained heteronanostructures. Results indicated that the size of Ni tip would increase when the quantity of gold precursor was reduced, while the size of Au tip would not change; it might result from the unchanged temperature which kept the size of Au tip being the same, but comparatively more Ni precursor led to continuous growth on Au nanocrystals. Besides, halogen ions could also tune the size of Au-Ni tips by bring down the surface energy of noble metal nanocrystals, when bromide-ions-containing didodecyldimethylammonium bromide (DDAB) was introduced to the system, Au particle in spindly nanostructures turned out to be smaller while the Ni size remained unchanged, and thus achieving the controllable regulation of both tips of the Au-Ni heteronanostructure under synthetic temperature of 240 ℃. To reducing both Au size and Ni size of the particles simultaneously, lower temperature in the initial reaction stage was used, but little rising of initial temperature did not produce remarkable changes of the size of Au-Ni heteronanostructure. This work not only provides a method for the size control of heteronanostructures, but also leads the material foundation for the further study of the catalytic performance of the Au-Ni bimetallic nanocrystals.