The optical turbulence forecasting by meteorological model can provide fundamental information for the flexible scheduling of observation and instruments of ground-based telescope, optimized the performance of adaptive optics and the opportunity of destroying object by laser. An optical turbulence forecast system has been established with the weather research and forecasting model. Based on this system and two optical turbulence parameterization methods, numerical model and analytical model, the meteorological parameters, C2n profiles and seeing at Ali site on November 06, 2011 are forecasted in advance on November 04, 05 and 06 respectively. Strong turbulence layers near ground, 2 km in boundary layer and 12 km in troposphere are discovered from the 6 forecasted results. The comparison between forecasted results and single star scintillation detection and ranging measurements shows that this forecasting system could provide the structure characteristics of Cn2 profiles. It also could provide the increasing trend of seeing results over night, similar to the result with differential image motion monitoring.