Process for preparing organoalkoxyhydrosilanes with a boron content less than 100 ppb and of the formula R1xHySi(OR2)z where x+y+z=4 and x, y, z are greater than or equal to 1, wherein, in a first step, a boron-contaminated organohalohydrosilane of the formula R1xHySiHalz where x+y+z=4, x, y, z are greater than or equal to 1, and R1 are linear or branched alkyl, cycloalkyl, aryl, alkenyl or arylalkyl radicals having 1 to 12 carbon atoms and Hal is F, Cl, Br or I, is subjected to a treatment with silica or aluminosilicate and the silica or the aluminosilicate is subsequently removed from the organohalohydrosilane in a second step and then the purified organohalohydrosilane is reacted with alcohol R2—OH where R2 is a methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl or tert-pentyl radical.