Meteorological drought can be converted to hydrological drought to a certain extent. In this paper, based on the monthly average precipitation data of Panjiakou Reservoir Basin from 1961 to 2010 and the inflow runoff series of Panjiakou Reservoir, the standardized precipitation index ( SPI ) and standardized runoff index ( SRI ) at the time scales of 1,3,6 and 12 months are calculated to characterize the meteorological drought and hydrological drought in the study area. Based on the conditional distribution model, the probability of meteorological drought in different time scales and different prediction periods ( or lag periods ) passing to different levels of hydrological drought in the future is analyzed. The results showed that when the SPI time scale was small or the prediction period ( lag period ) was short, the drought level of the converted SRI was more inclined to maintain the same drought level as that of SPI. With the increase of SPI time scale or the extension of prediction period ( lag period ), the drought level of the converted SRI was slightly lower than that of meteorological drought or returned to normal state.