Light solidification is a photochemical reaction between the light beam and photosensitive resin, and has a direction relation with light solidification micro-machining resolution. First of all, the movement trajectory of photon in the resin was traced by Monte Carlo simulation. By sampling the exposure photon in the incident and transmission processes, micro light beam solidification model was constructed based on photon transportation theory. Secondly, optical parameters of the resin were reconstructed by combining the genetic algorithm and the curing results of experiment. Finally, the simulated calculation of single-point curing process (λ=365 nm), shape and size of solidified points was carried out, and the as-obtained curing rule was analyzed in different exposure energy. The simulation results agree well with the experimental results under same exposure parameters. Thus the model can effectively simulate the complicated process of the reaction between the micro beam light and the resin, predict the curing result with different curing conditions and provide a foundation for studying micro solidification mechanisms, and optimizing the technique.