A novel design of micro-fluidic structure has been proposed to facilitate passive methanol supply and ventilation of carbon dioxide in direct methanol fuel cells (DMFC). Experimental study was conducted for three in-house fabricated cells which have different membrane-electrode-assemblies (MEA) and cathode-side air-breathing current collectors. Low rate of passive methanol supply and control was accomplished through capillary-force-driven mass transfer in the in-plane of carbon paper wicks. The low methanol supply rate using this passive method only meets the need of fuel of the electrochemical reaction, and there is almost no surplus methanol that could cross over the membrane. The micro-fluidic structure on the anode plate also makes passive removal of the CO2 gas from the electrochemical reaction. The influence of the concentration of methanol and cell operation temperature was examined and compared in the study. The results reveal very promising performance in the passive DMFCs when a methanol concentration is above 8M.