For a long time, there has been a practice that sets the phenomenalism of the middle aged Leibnitz against the monism of the old-aged Leibnitz in the international studies of Leibnitz. Contrary to this tendency, the paper demonstrate that monadism is the metaphysical objective of the phenomenalism of Leibnitz in terms of substance, the force-ontology and the theory of perception of Leibnitz on the basis of examination of the theoretical background of the phenomenalism of the middle-aged Leibnitz. Then the author show and demonstrate that the fundamental mediums of inter-relatedness of phenomenalism and mondism of Leibnitz from the doctrines of two kinds of substance, of matter and of force of Leibnitz. At last the paper concludes that only by adopting a kind of position and horizon of macroscopic holism and poly-layer,can it reach an unitary understanding and explanation of the phenomenlism and monalism of Leibnitz.
