Single-nanowire solar cells with a unique light-concentration property are expected to exceed the Shockley–Queisser limit. The architecture of single nanowire is an important factor to regulate its optical performance. We designed a trilobal silicon nanowire (SiNW) with two equivalent scales that possesses superior light-absorption efficiency in the whole wavelength range and shows good tolerance for incident angle. The electric field distribution in this geometry is concentrated in the blade with small equivalent scale and pivot with large equivalent scale, respectively, in the short wavelength range and long wavelength range. Corresponding good light absorption of trilobal SiNW in the two wavelength ranges leads to stronger total light-absorption capacity than that of cylindrical SiNW. Trilobal single-nanowire solar cells can obtain a short-circuit current density ($J_{\mathrm{SC}}$) of $647\mathrm{mA}·{\mathrm{cm}}^{?2}$, which provides a new choice for designing single nanowire with excellent light-capture capability.