This article studies how demography affects the outcome of the environmental policy in a macro-economic perspective, incorporating age-earning profiles in an OLG model à la Blanchard (1985) to capture the age structure effect of the demographic shocks. It first demonstrates, conversely to previous works of the related literature that a decrease in the birth rate may lower the steady-state per capita stock of physical capital even if the aggregate labor supply is exogenous. It also demonstrates that the ageing of population influences the macro-economic impact of the environmental policy according to the cause of the ageing and the life-cycle earnings assumption. Thus, with decreasing age-earning profiles, a lower birth rate reduces the detrimental impact of the environmental policy on the steady-state per capita stock of physical capital for low values of this birth rate, while a reduction of the mortality rate reinforces the negative outcome of the environmental policy. When earnings profiles are independent of age, ageing always strengthens the negative impact of the environmental policy.