Based on the ability to attenuate thermal radiation of droplets, water curtain plays an important role in fire prevention in the oil and gas terminal, traffic tunnel and other outdoor spaces. Radiation transfer characteristics of large droplets are determined by the Mie theory, and the Two-flux model is used to simplify the radiative transfer equation. Combined with an empirical formula to calculate the droplet diameter, a novel method is given for calculating the transmissivity of water curtain. Based on the method, influences of both the pressure and the width of water curtain on the transmissivity are fit for exponential relationship. Compared with experimental data, an ideal agreement is found between calculation results and experimental data for both single pipe water curtain and double pipe water curtain, only in the case of triplex pipe water curtain the deviation between calculation and experiment is more than 25%. A better calculation result can be obtained under the condition of the optical thin media. The method is effective in the scope of that the transmitted radiation is stronger than the environmental radiation. (C) 2016 Elsevier Ltd. All rights reserved.