A triangular lattice is proposed as the basis of the 1 550 nm-band photonic crystal structure. We use a duty cycle r/a=0.3 in order to achieve the greatest band gap. Using the combination of point defect and line defect, we propose lateral coupling structure. With the simulation calculation based on the FDTD Rsoft software, the defect mode, transmission spectra and steady-state time domain response are analyzed. At last, the insertion loss, extinction ratio and response time of the optical switch are calculated. The results show that the insertion loss, extinction ratio and other performance of the structure of the optical switch are better, and it can fully meet the requirements of modern applications.