A method has been elaborated for experimental determination of the components of the local velocity vector and of its modulus in a gas stream flowing through a tube packed with granular bed. The method was employed in novel experimental analysis of the flow held structure in the isothermal gas stream at the inlet and at the outlet cross-sections of the bed packed randomly of spheres in a tube. The impacts of the gas flow rate, the sphere diameter and the bed height on the formation of the radial profiles of the velocity vector and of its components at both cross-sections were investigated. On the ground of the experimental data the radial profiles of the gas interstitial velocity within the bed were evaluated according to the Dupuit-Forchheimer hypothesis and they were analysed in relation to the parameters mentioned above.