The plate-type methanol steam reformer (MSR) designed for improving its reforming performance is integrated with proton exchange membrane fuel cells (PEMFCs) regarded as a hopeful miniature power source. This study then uses computational fluid dynamics (CFD) through SIMPLE-C algorithm and Arrhenius form of reaction model to study the reforming performance of a plate-type MSR with the cylindrical cavities installed on the bottom of reformer channels. The influences of depth and diameter of cavities, and heated-wall temperature on reforming performance of reformer and estimated net power output of PEMFC have been examined with the same catalyst and inlet conditions in various flow channels of plate-type MSR. The results display that the installation of cylindrical cavities obviously improves the methanol conversion rate and hydrogen yield of a plate-type MSR. Compared with the traditional plate-type MSR, installing the cylindrical cavities of D-C = 1.4 mm and H-C = 1.5 mm on the plate-type MSR channels leads to the best enhancement in the methanol conversion rate by 22.65% and in the hydrogen yield by 64.52% at T-heater = 250 degrees C. Moreover, the novel plate type MSR with the cylindrical cavities of D-C = 1.4 mm and He = 1.5 mm acquires the best augmentation of 22.46% in the estimated net power output of PEMFC at T-heater = 250 degrees C.