Due to different phase delay of light wave propagating through waveguides with different length, wave front can be modulated by waveguide array. Based on theoretical derivation, the focused wave can be obtained through triangular waveguide array. Using the finite-difference in time-domain method, the focusing in the convex triangular waveguide arrays is simulated, and the results agree with theoretical derivation well. Simulation results also indicate that the concave triangular waveguide array can split the beam.