Abstract: In order to study the influences of prestressing degree on curved box-girder bridges,180 two-span curved box-girder bridge models were built by taking bridge length,central angle and prestressing degree as parameters.Data-fitting was made with two-step one-parameter method,resulting in experimental formulas of stresses and unit displacements in control sections under limit states,so variation trends and degree varying with prestressing degree were studied.Formulas of prestressing degree in section were proposed;two indexes were advised to reflect the variation trend and degree of structural reactions varying with prestressing degree.