The invention discloses an oblique section bending calculation system of a pre-tensioned plate girder bridge, and relates to the technical field of highway bridge structure calculation and analysis. A data input module inputs various data to a computer; a data check module checks the completeness and the logic of the various input data; if all the input data are accurate, a calculation module calculates the various input data; if the various input data are incomplete or wrong, an error prompt module prompts error information; a modification module modifies the various input data according to the prompted error information till no error information; the calculation module calculates the length of horizontal projection, the value of shear combined design, the height of a pressed zone and bending bearing capacity of an oblique section according to the various input data; and a data output module outputs calculation result forms, result graphs and calculation sheets. The calculation efficiency of the plate girder bridge is improved; and calculation of multiple sections can be performed on a girder body at the same time.