In this paper, we present a study on D–H (7Li) plasmas with moderate hydrogen concentration (∼15%) on the HT-7 tokamak. Enhanced density fluctuation induced by ion cyclotron range of frequencies (ICRF) at the centre of the plasma is observed by a continuous wave CO2 (λ = 10.6 µm) collective scattering system. At the same time, the Doppler shift VD due to plasma rotation in the mode-converted ICRF D–H (7Li) plasmas is observed experimentally for the first time on the HT-7 tokamak, and the Doppler shift VD is approximately linear versus the change in plasma stored energy ΔW.