According to the optimization problem of the cooling channels a conventional journal bearing, the thermohydrodynamic(THD) mathematical model of the journal bearing was set up and the numerical solution was done combined with ANSYS. Considering the effects of the internal cooling channels in the pad on controlling the working temperature effectively by convection, the narrow space in the pad was made full use to form network type internal cooling channels in the pad. The calculation model set up in this paper was then applied to the THD analysis of the original and the improved journal bearing models. The obtained results show that the working temperature of the pad is obviously improved by the internal cooling channels. And then the working temperature of the pad under different convective heat transfer coefficients were studied. It was found that the overall working temperature on the inside surface of the pad decline significantly with an average decline 2 ~ 3°C, as the convective heat transfer coefficient of the internal cooling channels is strengthened from 200W/m2·K to 500W/m2·K.