As a representative of new energy in the production end of ubiquitous power Internet of things, photovoltaic power generation has a very broad development prospect. At present, distributed photovoltaic has been widely used. Taking Zhejiang as an example, the majority of new users belong to low -voltage distribution network every year. Photovoltaic power generation system is composed of photovoltaic modules in series and in parallel. In order to study several common faults and their effects in photovoltaic system, a simulation model is built according to the parameters requirements of low-voltage photovoltaic system in national grid. The output of photovoltaic system under four common faults is simulated. It is concluded that there is only one of the four faults. When there are four kinds of faults in photovoltaic cells, open circuit has the greatest impact on the output power, followed by hot spot, short circuit, and aging.