The surface temperature of PV is different in the condition of the different shadings; the corresponding output characteristics will be different. This paper studies the influence of temperature and shading variation on the output P-V and I-V characteristics of photovoltaic array, and the effect of this difference on the global MPPT algorithm. In order to analyze the influence of temperature and shading on the output characteristics of photovoltaic array, the article assumes that a cloud drifts across the PV array, and simulate three kinds of situations. Simulation results show that, the output power decreased slightly under the different temperature and shading, but closer to the actual situation. The results will provide theoretical support for further optimization of global MPPT algorithm.