Abstract: The output characteristics of photovoltaic power generation are different from that of conventional generating units. With increase of installed capacity of photovoltaic power generation in Tibet,the safe and stable operation of Tibet power grid is facing severe challenges. According to the operation data in the winter of 2019,based on the power system analysis software package（PSASP）,the electromechanical simulation model of Tibet power grid containing with large-scale photovoltaic power generation is established. This paper analyzes the influence of typical light disturbance,photovoltaic power station cut-off and short-circuit fault on the transient stability of the grid. The analysis shows that the power grid is capable to maintain transient stability under the conditions of typical light disturbance,photovoltaic power station cut-off and short-circuit fault,but some bus voltages are higher than the upper limit of the specified voltage. To address the problem,the reactive power compensation device should be installed to eliminate the over-limit voltages of some buses,which helps to improve the voltage stability of the grid system.