To obtain an optimum structure of all-optical switch, based on 90° photonic-crystal bend waveguide, an improved photonic crystal structure with Kerr nonlinear dielectric rods is introduced. By means of finite difference time domain (FDTD), the numerical analysis shows that this switch can achieve the following performance: bandwidth (about 50 nm), high extinction ratio (>40 dB), threshold power density (5.2 W/μm). At the same time, it can also implement fundamental logical functions.