oxidation state of oxygen in Hydrogen peroxide is
-1
The oxidation number of oxygen is -2 in most of its compounds , except in peroxides like H2O2,BaO2 etc. where it is -1
1.Another interesting exception is found in the compound OF2 (oxygen difluoride) where the oxidation number of oxygen is +2
2.This is due to the fact that fluorine being the most electronegative element known has always an oxidation number of -1.