We investigated the performance of YBa2Cu3O7-x (YBCO) membrane reactor in the process of partial oxidation of methane (POM) to syngas. When Ni/ZrO2 catalyst was used the CH4 conversion and CO selectivity could reach almost 100% and 95%, respectively, and the oxygen permeation fluxes could reach 1.5 ml min(-1) cm(-2) at 900 degrees C. The YBCO membranes reactor also showed self-catalytic properties; without any catalysts the CH4 conversion and CO selectivity could reach about 28% and 90% at 900 degrees C, respectively. However, the stability of YBCO membrane was not desirable because of the reduction of copper from the YBCO membrane. The reaction mechanism of POM in YBCO reactor was also discussed based on the influence of space velocity (SV) on CO selectivity. The indirect partial oxidation mechanism may be the dominant mechanism of POM process in the YBCO membrane reactor. (c) 2006 Elsevier B.V. All rights reserved.