Six tobacco（ Nicotiana tabacum）genotypes were selected as the parents of P（×P- 1）/2 incomplete diallel cross to determine combing ability and genetic model of stomatal conductance on tobacco leaves and disease resistances to weather- fleck. The results showed that genetic characteristics of stomatal conductance on the lower epidermis of tobacco leaves and resistance to weather- fleck was of additive- dominance genetic models. Recessive genes controlled disease resistance and small stomatal conductance,，and dominant genes controlled disease susceptibility and big stomatal conductance. Susceptible genotypes possessed high positive GCA which was negative in resistant genotypes.