In order to study the influence of altitude, temperature and runway contamination on takeoff performance of large civil aircrafts, theoretic analysis as well as model calculation was used to deduce the relationship between airport condition and takeoff field length. Firstly, several main factors were introduced and analyzed, which were airport altitude, temperature, runway condition, SLST (sea level static thrust) and high lift device. Secondly, a calculation model which can automatically satisfy the airworthiness requirement of airliner takeoff was developed. Thirdly, takeoff performance at different airport conditions was calculated with this model. Finally, the data was summarized and several types of charts were provided as reference for aircraft designers and operators.