In this paper, the effects of non-isothermal and gravity on inner methanol concentration and thermal distribution of passive micro direct methanol fuel cell (mu DMFC) are taken into account to improve the cell performance. A whole two-dimensional model coupled with the mass transfer, the momentum transfer and the heat transfer is established. Simulation results show that both more uniform reactant concentration and higher in reaction temperature are obtained with the gravity effect. Furthermore, a passive mu DMFC with the active area of 1.0 cm(2) is designed and fabricated. The detailed experimental validation is conducted to evaluate the inner transport characteristic as well as the corresponding cell performance. Experimental results reveal that when the cell is supplied within a certain concentration range, both the peak power density of cell and cell energy capacity with gravity positive effect is much higher than that without gravity effect. In addition, the anode CO2 emission and cathode water-flooding of the passive mu DMFC are analyzed, and the experimental results are in good agreement with the simulation. (C) 2018 Elsevier Ltd. All rights reserved.