The invention relates to a power grid wide area voltage control method, a power grid wide area voltage control system and power grid wide area voltage control equipment. The power grid wide area voltage control method comprises the steps of acquiring synchronous voltage values of multiple bus lines; selecting the minimum voltage value in the multiple synchronous voltage values, and calculating the difference value of a preset threshold value and the minimum voltage value; acquiring an additional voltage value according the difference value of the preset threshold value and the minimum voltage value; acquiring a regulated voltage reference value according to the additional voltage value and the primary voltage reference value of an electric generator, and sending the regulated voltage reference value to an excitation system of the electric generator so as to regulate the machine end voltage and output reactive power of the electric generator. By taking the additional voltage value as the feedback, the voltage reference value of the excitation system of the electric generator is regulated, so that the regulated voltage reference value is obtained and is sent to the excitation system of the electric generator, the electric generator can feel the voltage of the bus lines, and the output reactive power is increased when the voltage is relatively low, so that the power grid wide area voltage can be continuously controlled, and further, the transient voltage stability of a power grid can be improved.