Exponential smoothing is an efficient method for forecasting and decision-making.  The forecasting model of exponential smoothing to forecast the displacement at Observation Point 5 of certain city hazardous landslide is applied in this paper. According to the characteristics of observation forecast formula with linear trend of the twice exponential smoothing,  appropriate formulae calculating at,  bt and suitable exponential smoothing value are selected and used to make a forecast. The forecast results show that the errors between the forecast values and the observation values are very little. And it shows that this model may be well applied to the forecast of the displacement in the deformation of slopes.