Firstly,we choose a strata temperature gradient and start to compute.According to thermodynamic parameters,mud fluid parameters and well casing structure parameters etc.,the exit temperature of mud fluid can be obtained.By comparing the calculated value with the measured value of the exit temperature,we correct the chosen strata temperature gradient.Sequentially,we do above_mentioned works repeatedly until a proper strata temperature gradient is gained.Based on this,derived from the equations of thermodynamics and fluid mechanics,we can obtain the temperature variation along the depth of sidewall,and the mathematical model of distribution of strata temperature.Since mud fluid,rock and the temperature field are interactive and interfering during the process of drilling wells,the above technique provides a new method for investigating the theory and applications of the coupled thermal_hydrological_mechanical processes.