The invention discloses an electric power system and an electric power market participant risk assessment system. The electric power system comprises an electricity quantity acquisition device, a line loss acquisition device, an input controller and a background processing device, wherein the electricity quantity acquisition device acquires the electricity consumption amount of a user and the transmission electricity quantity of each level of power grid; the line loss acquisition device acquires a line loss electricity quantity; the input controller inputs the name of an electricity quantity to be determined; and the background processing device calculates the electricity quantity to be determined. The electric power market participant risk assessment system also comprises a market acquisition device, a model establishment unit, an index determination unit, an index screening unit and a pressure test unit, wherein the market acquisition device acquires market information data; the model establishment unit establishes a behavior model of the electric power market participant; the index determination unit determines a pressure-bearing index and a risk index; the index screening unit screens a key risk index which has a high influence degree on a pressure-bearing index variable; and the pressure test unit evaluates the risk to which the participant faces under an extreme condition. Therefore, through the flexible acquisition of the electricity quantity and the pressure test, the risk to which the electric power market participant faces under the extreme condition can be effectively evaluated.