The objective of this study is to analyze the performance characteristics of the direct methanol fuel cell (DMFC) using air or oxygen as the oxidant gas at various operating conditions. In order to investigate the effect of various operating parameters on DMFC performance, experiments were performed with various parameters including cell temperature, methanol concentration, flow rate, cathode humidification temperature, and cathode backpressure. The membrane electrode assembly (MEA) used Nafion 117, by loading a Pt-Ru (4 mg/cm(2)) catalyst at the anode and Pt-black (4 mg/cm(2)) catalyst at the cathode. The performance of the DMFC was analyzed with a polarization curve, which was measured with the voltage-current density and power-current density. It was revealed that the performance of the DMFC was enhanced by increasing of the cell temperature, cathode flow rate, and cathode backpressure. Also, the methanol diffusion and transfer conversion rate of the fuel cell are analyzed by using the effective mass transfer coefficient and Damkohler number under various performance parameters. The comparison of the performance with both air and oxygen showed that using the oxygen resulted in higher performance than that of air by the active electrochemical reaction.