LIBS of aluminum under the ambient pressure from 1 atm to 10 Pa were implemented. Results showed that the temperature of plasma increased with the decreased pressure and leaded to the raise of density of Al II, decrease of density of Al I. Furthermore, in order to understand the influence of air flow to quantification of LIBS an alloy of aluminum and silicon was measured by LIBS under different level wind. Results showed the ratio of Si I/Al I which is important in quantitative analysis changed with wind despite the pressure change a little. Therefore, the ambient atmosphere must be steady enough in order to improve the accuracy in quantitative analysis of LIBS.