Abstract：The propagating path of satellite signals through the atmosphere is a curve which is difficult to precisely plot．In order to precisely calculate the correction to its curvature we take a fold line as the ap proximation of]st degree to the refractive curve，then divide the fold line into several sections．Thus the re— fractive curve can be approximated by circular arc．According to the above consideration， a series of strict formulae to calculate the curvature correction under the condition of different zenith distances are derived. At last，a model which is convenient and precise for calculating the curvature correction has been established．
