Using the laser absorption spectroscopy and algebraic iterative reconstruction methods, two-dimensional (2D) temperature distribution has been reconstructed with irregular beam distribution. The reconstruction accuracy strongly depends on the beam distribution. Therefore, an optimal design of the beam arrays can reduce the experimental cost and maximize the beam potentiality. This paper introduces the grid weight factor (GridWF) to evaluate the beam distribution relating to the discrete region. The error of the reconstruction is less than 15% using optimal beam distribution, which is lower than the results of non-optimization. As an increase in the number of emitters, the error can be obviously reduced. Two H2O absorption transitions (7205.25 cm −1 and 7416.05 cm−1) are adopted in the simulation. The 2D temperature reconstruction with optimal beam distribution and different number of emitters are demonstrated, showing the optimal design of the beam array having excellent reconstructed performance.