Abstract: Given that the law of heat conduction and technique of stepwise refinement are utilized to tackle the problems of thermal protective clothing, for instance, temperature distribution and the thickness of each layer in high temperature environment, hence one-dimensional heat transfer model and optimization search models in multilayered medium are established. Firstly, in accordance with the characteristics such as the continuity of temperature and equal heat transfer rate between front and back interfaces of different layers of protective clothing, this paper has set up the partial differential equation of heat transfer in multilayered medium and the corresponding initial and boundary conditions after a combination of one-dimensional heat transfer equation. In order to determine the parameters in proposed models, this paper has established a stepwise refinement model by adopting the variable step search algorithm. Secondly, the finite difference method based on C-N scheme is applied to numerically solve the definite problem model and obtain the temperature distribution from the outer layer of clothing to human skin. In order to determine the thickness of each protective layer that meets the temperature conditions, this paper has established the optimization model based on the thickness of the protective layer, and obtains the optimal thickness by applying the variable step search algorithm in numerical solution. Finally, sensitivity analysis of the model is carried out to verify the stability and feasibility of the model.