This paper is helpful to the design of photonic-crystal Vertical-Cavity Surface-Emitting lasers which emit single transverse mode.We use the theory of the single transverse mode of photonic crystal fiber in the analysis of the normalized frequency varying with the change of the lattice constant and the value of r/a.We calculate the band-gap of the two-dimensional air holes photonic crystal with triangular structure by the finite-difference time-domain method.In order to achieve single-transverse mode lasing，we use the calculation results to select the appropriate parameters of the photonic crystal structure.We use the rate equations of the carrier surface density and photon number surface density to analyze the influence of each photonic crystal structure parameters.