The results of an experimental research of ion megawatt beams are submitted. The radiation intensity of Balmier atom a -line of deuterium (l = 656.5 nm) and hydrogen (l = 656.3 nm) raised at passage of ion beam through residual gas in the chamber of installation was measured. On optical measurements of the beam sizes, situation of its center and beam divergence and also distribution of integrated current density in cross section were determined. The data measured by optical method are used for research of radiation intensity dependence from current density and beam duration with the account of gas pressure change in the chamber. The offered technique is successfully used as monitoring powerful ion beam.