The invention discloses a data acquisition on-demand mutual preparation method for isomorphic power dispatching automation systems. Under the condition of not increasing communication channels at a plant end, by comparing plants collected by the isomorphic power dispatching automation systems, the data acquisition on-demand mutual preparation method automatically provides local or entire data acquisition automation mutual preparation functions of the systems for the jointly collected plants, and therefore current data acquisition resources of multiple isomorphic systems are effectively used, and the risk resistance capacity of the systems is improved.