[en] Possibility of measuring mean height of surface roughness, using γ-radiation, reflected from rough surface, is considered. The problem of measuring mean height of surface roughness is reduced to determination of mean square deviation value σsub(x)sup(2). Algorithm of σsub(x)sup(2) determination is described in detail; evaluations of mathematical expectation and dispersion are used in it. It is stated, that σsub(x)sup(2) error depends on anti x value, and it decreases with the growth of measuring point number. Evaluation of approximated expression for σsub(x)sup(2) dispersion has shown, that at 6% error of measuring roughness mean square deviation, summary measuring time of 200 s order at 0.1 s duration of one measurement and mean counting rate of about 10⁵ pul/s is required