The coefficient model of small scale thermal mechanical dispersion of saturated porous aquifer is established and it is applied in the heat transfer process of convective dispersion. Step-by-step test is conducted for the two physical processes of one-dimensional unsteady heat conduction of semi-infinite medium and convection dispersion to obtain heat physical parameters, thus achieving the verification purpose of analytical solution. On this basis, the porous aquifer thermal dispersion effect is evaluated, the results show that if coefficient of thermal mechanical dispersion 1 x 10(-2) W m(-1) K-1 is selected as the critical point where thermal transport is affected, the distribution of thermal mechanical dispersion coefficients can be divided into non-ignorable triangular domain and ignorable polygon domain. However, the result shows that the maximum of longitudinal dispersivity is at centimeter order of magnitude, which is significantly different from the research result of thermal dispersivity under outdoors large scale conditions. This proves the existence of scale effect of thermal dispersion, and thus shows the direction of further research. At last, under condition that the thermal dispersion is ignored, the heat transfer method of thermal transport under conditions of different seepage velocities is also defined. (C) 2014 Elsevier Ltd. All rights reserved.