A seven-channel NaI(Tl) detector array installed on an HT-7 superconducting tokamak has been used to detect the hard X-ray (Ehν>20 keV) emitted from the plasma. The physical mechanism of the lower hybrid waves propagating and absorbed in the plasma is investigated by the measurement of the hard X-ray radial profile at different discharge parameters. © 2001 Chin. Phys. Soc. and IOP Publishing Ltd.