The invention provides a method and system for evaluating the stability of a photovoltaic power station system. The system comprises a cloud monitoring platform large data processor, a data collector, an outdoor test device, an intelligent combiner box and an environment collector. Different inverters uploads operation data, operation status, temperature, humidity and light intensity to the cloud monitoring platform large data processor through the data collector, wherein the temperature, humidity and light intensity are collected by the environment collector. The cloud monitoring platform large data processor calculates the generating capacity and operation data of a power station in real time, so as to compare the generating capacity differences of inverters of different manufacturers. The system uses the difference control algorithm of photovoltaic power station inverters of different manufacturers, a photovoltaic module health analysis algorithm and a fast photovoltaic power station failure rate detection and control algorithm to carry out evaluating, which provides a favorable reference for the effective management and predictive control of the photovoltaic power station.