In recent years, distributed photovoltaic（PV）systems have entered a period of rapid development. Affected by the site environment, the distributed PV system is vulnerable to the nearly shadows during operation, resulting in loss of power generation which affecting demand side energy management. The generation performance of distributed PV system under the influence of nearly shadow is simulated and analyzed. The influence mechanism of shadow on the output characteristics of PV array is studied, the loss of power generation due to shadow is quantified, and the PV array engineering model and occlusion model are established. Based on this, combined with the annual solar position algorithm, the annual power generation of a distributed PV system under shadow is simulated, and the power generation loss and the economic loss of the distributed PV system before and after shadow is analyzed. The results can provide a reference for the design and planning of distributed PV system.