The invention provides a method and a system for obtaining a flicker transmission coefficient of grid connection of photovoltaic power stations and defines subtransient reactance of a photovoltaic current transformer by considering that the frequency characteristic of impedance of the photovoltaic current transformer is similar to the subtransient reactance of a synchronous power generator and the subtransient reactance of an induction motor. Furthermore, the subtransient reactance of the photovoltaic current transformer can be obtained by utilizing parameters of the photovoltaic current transformer, so that the flicker transmission coefficient between any two nodes in a multi-port network diagram of a photovoltaic power station group, namely the flicker transmission coefficient of grid connection of the photovoltaic power stations, can be accurately obtained, and the difficult problem in the prior art can be further solved.