The influence of the chemical order on the viscosity of liquid alloys is investigated by numerical simulation of molecular dynamics. The temperature and composition dependence is discussed in the case of two contrasting alloys: K-Cs and Li-Bi. These two mixtures have different chemical orders, the first one being random and the second one having strong heterocoordination tendencies. In the case of K-Cs, the behavior of the mixture vs temperature is similar to a pure system and its viscosity varies monotonically with the composition. It is not the case for Li-Bi due to its marked chemical order and the heterocoordination tendency is accompanied by a maximum of the viscosity of the mixture when the composition is changed. For the first time, estimates of the temperature dependence of the viscosity of three representative Li-Bi alloys are given.