Results of researches of physical and chemical bases of process sublimate clearings of molybdenum trioxide from uranium oxides at the lowered pressure are resulted. Equilibrium compositions in system МоO₃—UO₂, kinetic constant, apparent energy of activation is defined by thermodynamic calculations and kinetic researches, rate-limiting step is established. The technological scheme of processing of molybdenum waste from uranium dioxide production, including following stages: crushing of molybdenum boats, oxidation of molybdenum by oxygen, sublimate clearing of molybdenum trioxide from uranium oxides and other accompanying impurity is offered on the basis of the received results.