Abstract: Output power of PV generation is undulatory and random.In order to improve the predictability of PV generation and accuracy of maximum power point tracking（MPPT）,it is necessary to study the shade effect on PV array’s output characteristics in depth.First,high dimension mathematical model of PV array was constructed based on PV module unit,which considering bypass diode and blocking diode effect.And a fast simulation algorithm for PV array’s output characteristic computing was proposed,that was applicable to different random shade conditions and easy to realize distributed computing.Simulation results under different shades demonstrate that PV array’s output characteristics are closely related to distribution area and irradiance of shade.Meanwhile output characteristics of PV array are affected by shade significantly.Computing time is approximately linear related to PV array scale,and computing speed could be advanced by adopting distributed computing or reducing total number of discreted points.The proposed algorithm,which has clear physical meaning and is easy to realize,is groundwork for analysis and control of practical PV arrays.