Abstract: In order to fulfill the requirement for astronomical observation in the optical-infrared band using large universal aperture optical telescopes, China is planning to construct a 12-meter large aperture optical-infrared telescope (LOT). LOT is of particular significance to Chinese astronomy and would be co-phased in the near-infrared waveband. The primary mirror of LOT will be constructed from either hexagonal segments or petal-shaped segments. Analysis of co-phasing errors using a segmented primary mirror tiled by petal-shaped segments for LOT has been presented. The proposed primary mirror of LOT has 72 petal-shaped segments and a 4.5-meter circular mirror in the center. Detailed theoretical derivation of co-phasing errors and simulation about out-plane errors separately and comprehensively have been provided. SR (Strehl Ratio) of LOT is greater than 0.8 when the RMS (Root Mean Square) value of normally distributed tip-tilt errors is less than 0.016^\prime\prime or the RMS value of normally distributed piston error is less than 42.5nm at the co-phasing wavelength 1μm. The simulation results are of great importance for the segmented primary mirror with active optics in LOT.