Weather condition is one of environmental factors influencing the sugar accumulation of wine grapes. Research shows that average air temperature, maximal air temperature, sunlight duration and temperaturehumidity ratio are four main weather factors affecting daily sugar accumulation from coloring stage to maturity stage. The daily sugar accumulation of grapes is optimal when average air temperature, maximal temperature, sunlight duration and temperaturehumidity ratio are 24.0 ℃, 29.3 ℃, 6.4 h and 0.35, respectively. At the range of less than these values，the daily sugar accumulation increases with these factors, and at the range of greater than theses values, the daily sugar accumulation decreases with these factors.