By matrix rotatable planning of experiment dependence of simultaneous influence of reactionary temperature, caustic concentration in spillage liquor and time of digestion for extraction of alumina from SUBR bauxite is investigated. The analysis of results of the lead researches allows to conclude it is necessary to consider as optimum temperature of SUBR bauxite digestion temperature 240-245 ^oС at 80 minutes of an exposition in autoclaves and caustic concentration of spillage liquor 240-260 g/dm³. In these conditions duration of bauxite autoclave digestion can be reduced in 1,5 times in comparison with existing production.