Measurements were carried out on Tibetan Plateau (Lhasa, 3648 m above sea level) with a multi-channel moderate bandwidth filter instrument during the period from June 24. to November 30., 1996. The analysis of preliminary data shows that hourly mean CIE-weighted biologically effective UV dose rate at local noon can reach to as high as 390.5 mW/m2. The corresponding average value was 225.4 mW/m2; Due to the combined effect of cloud cover variation with ozone variation, the increasing trend of this UV dose rate exists during this period of measurements. The relation between the ratio of irradiance close to noon at 340nm to that at 305nm and total ozone column shows that the variation of total ozone column may also cause the variation of UV radiation. In addition, the UV dose rate in the morning is slightly higher than that at afternoon with same solar zenith angle.¿ 1997 American Geophysical Union