Due to the difference in phase delay of light wave propagating through waveguides with different lengths, wave front can be modulated by waveguide array. Based on theoretical derivation, it is found that metal waveguide array with convex triangle in left and right sides can focus light wave. Using the finite-difference time-domain method, the focusing in metal waveguide array with convex triangle in left and right sides is simulated. It is found that when the thickness of waveguide h=6000 nm, the difference in waveguide length d=100 nm, the waveguide number m=10, and the waveguide width w=100 nm, the metal waveguide array has better focusing performance. Some valuable characteristics of such a structure are also found by investigating the of different framework parameters on its focusing properties. Simulations also indicate that when the waveguide width w2=80 nm, the central waveguide width w1=150 nm, the difference in waveguide length d=200 nm, the thickness of the waveguide h=4400 nm, and the waveguide number m=8, the concave triangular waveguide array can realize beam splitting.