Simultaneous hydrogen formation and purification can accelerate the reaction rate, leading to a higher conversion or lower reaction temperature than that of traditional processes. The steam reforming of hydrogen-rich fuel with a membrane reactor shows comprehensive competitiveness in hydrogen industry. However, the research of membrane reformers with external heat supplement under unsteady state is still unclear. A 1-dimensional non-isothermal heterogeneous unsteady state model was established to analyze methanol steam reforming using a double-jacketed membrane reactor (Fig. 1). Methanol oxidation provided the heat for steam reforming, while hydrogen permeated through a palladium membrane. The species molar fractions and reformer temperature were analyzed under co-current and counter-current operation between oxidation and reformer sides. The co-current operation outperformed the counter-current because the co-current case showed higher conversion and reformer temperature. The start-up of reformer was simulated under two conditions: (1) the catalyst temperature was 433K, and the inlet temperature was 543K; (2) the catalyst temperature was 543K, and the inlet temperature was 433K. The results revealed that both conditions reached thermal equilibrium within 150 dimensionless time. Condition (1) yielded higher conversion and reformer temperature than condition (2) at steady state. Condition (2) had higher conversion than condition (1) in the beginning. Using hot steam as the reformer heating gas could decrease the time required for the preheating period. Two strategies were compared to analyze the reformer response when temporary extra hydrogen was required. The results showed that increasing methanol flow rate outperformed increasing reformer temperature.