To find out the influence rule of micro-pore geometric characteristics in the confined forming chamber on the propagation properties of the curing light source, and then analyze and predict the manufacturing accuracy in stereolithography process, numerical study was done using FDTD software to obtain the light transmittance of the substrate machined micro-pore array and the characteristics of light energy distribution in the curing zone. The simulation results were verified by experiments. The research results show that the shape, size and period of the micro-pore formed in the constrained substrate affect the light transmittance and the light intensity distribution in the forming area. Compared with the shape of the micro-pore on the substrate, the size and period of the micro-pore show a more significant effect, in which, reducing the size and period of the micro-pore facilitate the light transmittance and the light intensity uniformity improvement. If the diameter of micro-pore is less than half wavelength and the ratio of micro-pore edge spacing to micro-pore diameter is less than 1:1, the negative effect of micro-pore can be reduced significantly. When the diameter of micro-pore is much larger than half wavelength, an undesirable additional feature on the surface of the fabricated part will be formed due to the micro-pore in constrained substrate and thus affecting the manufacturing accuracy. The results can provide direction and theoretical basis for the improvement of substrate preparation process.