The invention relates to a power generation margin distribution method for a photovoltaic power station based on power grid security constraints and belongs to the field of running and control technologies of new energy electric power systems. The power generation margin distribution method for the photovoltaic power station based on power grid security constraints includes that according to a fair scheduling principle, after the photovoltaic power station enters a free power generation state, the space of a power grid for performing photovoltaic power generation is uniformly distributed for each photovoltaic power station according to a minimum load rate deviation method, on the one hand, unnecessary photovoltaic power discarding due to a too small active set value of the photovoltaic power generation is avoided, and on the other hand, the problem that the power output by the photovoltaic power generation surpasses the power grid bearing capacity due to a too large active set value due to distributing the photovoltaic power generation capacity is avoided. The power generation margin distribution method for the photovoltaic power station based on power grid security constraints is integrated in a photovoltaic power generation active control master station run by a dispatching center to enable the system to implement an optimal control strategy in real time according to the photovoltaic power generation running state and the power grid running state, maintain enough backspin security space for the power grid, guarantee the active power security of the section of a connecting wire of the photovoltaic power station and the power grid and guarantee the fair scheduling among the photovoltaic power stations.