The　bridge　length　and　central　angle　are　taken　as　the　parameters　to　build　30　two-span　curved　box-girder　bridge　models.　The　explicit　experimental　formulas　between　the　normal　stresses　of　corner　points　in　control　sections　under　different　loads　and　the　two　parameters　is　fitted　with　the　nonlinear　function　method.　The　sign　relationship　between　variables　is　used　to　show　the　variation　trends　and　degrees　of　normal　stresses　influenced　by　those　parameters,　and　the　rules　of　the　normal　stresses　changing　with　the　parameters　under　different　loads　are　qualitatively　and　quantitatively　discussed.　Advices　are　finally　provided　for　engineering　design.