It is very difficult to employ only inertial effect to separate the 0.5-1 mu m submicroparticles each other. Therefore, the thermophoretic sorter with expansion-contraction microchannel is proposed to separate the submicroparticles. Numerical simulations are carried out to obtain the particles' trajectories for different inlet velocity, different sheath flow rate, different expansion-contraction ratio of the channel, different wall temperature difference. The results show that it is feasible to sort the submicroparticles with different sizes by thermophoresis. Smaller inlet velocity, greater wall temperature difference, lower sheath flow rate, and greater expansion-contraction ratio of the channel can make the separation efficiency better. In addition, the comparison of numerical results and experimental results show good agreement. The preferential parameters of thermophoretic sorter are confirmed based on the numerical and experimental results. (C) 2019 Elsevier Ltd. All rights reserved.