First mirror ig the reflect mirror in optic diagnostic system.More than 80 pieces of metal mirrors would be used in ITER diagnostic systems.The reliability of the optic signal depends largely on the surface performance of the mirrors.Tungsten (W)、molybdenum(Mo)and stainless steel(SS)are the three candidate metal mirrors.The present work describes the preliminary experiments of these three mirrors exposed in the vacuum chamber of the HT_7 tokamak during autumn plasma discharge in 2009.One SS mirror was mounted near the Thomson scattering diagnosis window(North) and the lower hybrid current drive(LHCD)system(South),the other W、Mo and SS mirrors were mounted near the ion cyclotron wave window in the HT-7 device.