The main purpose of current work is constructing the evolutionary model of influenza epidemic in urban population and estimation the impact of the preventive measures to the population. Also in this work we select risk-group from the population and research the epidemic process in it. Total urban population and risk group are divided into three subgroups Susceptible, Infected and Recovered and during the epidemic individuals transfer from one subgroup to the other. During the epidemic season the quantitative structure of the subgroups is changed, but these changes could be different in risk-group and in vaccinated subgroup. In the model we assume that vaccination company occurs before season epidemic of influenza begins, to avoid repeated infection of vaccinated individuals. We construct an evolution of epidemic and take into account vaccination and infection expenses, from the society point of view. Numerical simulation are also presented in the paper.