Abstract: Plot culture of tobacco (K326) was carried out to study. The results showed that synergist improved the contents of chlorophyll. The content of chlorophyll was highest is treament C, and lowest in CK, but no significant difference under the condition of decreasing the fertilizer application. Net photosynethsis and water use efficiency were improved; stomatal conductance (Gs) and intercellular CO2 concentration (Ci) were decreased by treatment of synergist. Transpiration rates (Tr) were not different significantly among treatments.