To improve the automation degree and provide a novel real-time, in situ measurement methods of optimizing real boiler control, tunable diode absorption spectroscopy (TDLAS) combined with computed tomography reconstruction was proposed by theoretical analysis and experimental validation. It was proved by simulation that the peak location could be reconstructed and the relative values could be distinguished in case of only two projections. Six measuring grid was arranged to obtain the reconstructed 2-D temperature distribution. The result showes that the correlation coefficient between the averaged temperature and load is 0.91. Linear regression analysis showes that the coefficient of determination is 0.88. The averaged temperature could represent the real-time total radiation, which can be used to avoid over adjusting and obtain the heat value. The 2-D temperature distribution can be used to leveling the boiler. It was concluded that this method provides important support to the non-intrusive in-situ temperature measurement and study of optimizing combustion control.