The Harder Narasimhan filtrations and rational contractions Zusammenfassung: In this paper we investigate the relation between of the relative tangent sheaf of a rational contraction between toric varieties and the Harder Narasimhan filtration of the tangent sheaf of the total space. On the course of the proof we give a combinatorial description of the terms of the Harder Narasimhan filtration of the tangent sheaf of given toric variety