The study of fractional Talbot effect of the 2D amplitude skewed array is very important to the designation and manufacture of the new type array illumination. The fractional self-imaging effect of the 2D array with arbitrary shape and symmetry is studied theoretically, using scalar diffraction theory and the known periodic self-Fourier-Fresnel transform function comb(x,y). As a result, a general equation to calculate the phase of the fractional Talbot image of the 2D array is also got. As an example, the intensity distribution of the 60° skewed diamond periodic array in different fractional Talbot planes is numerically evaluated using Matlab. The result is a good agreement with the theory. Based on the theory, the reliability of the designation and manufacture of this skewed diamond array illumination is briefly discussed. Additionally, comparisons of the characteristics are made for the 2D amplitude skewed array and the 2D amplitude orthogonal array in the compression ratio and shape of the light spot.