We developed a model demonstrating that the increase of fuel utilization and fuel concentration is the key to achieve the high energy density direct methanol fuel cell system. We also explain that fuel utilization and fuel concentration are closely related to crossover of methanol and water. A method that measures the methanol crossover, water crossover, and methanol utilization is presented. Unlike conventional methods, this method is not affected from the ambiguous CO2 crossover effect through electrolyte membrane since the method is based on the methanol/water measurement at the inlet and outlet of anode and cathode. Methanol and water crossover, methanol utilization, and methanol to electricity conversion rate were measured as a function of current density, fuel concentration and anode/cathode flow rate in a single cell.