In modern construction the precast method is preferable because of it has many advantages s than the cast in situ concrete structure like it needs less work on site, better control of component quality, rapid construction, and good economic and environmental benefits. One of the methods of precast concrete structure is segmental post tensioned structure which is important for bridge and other mega projects. Reinforced concrete structures are affected by fire and the effect of this fire on the load carrying capacity and deflection is not consider in previous design works and in building codes. But this proposed thesis tries to investigate numerically the effect of post fire behavior on post tensioned segmental concrete beam by using finite method analysis software ANSYS. The objective of these thesis is analyzing numerically the effect of post fire behavior of post-tensioned segmental concrete beam under static loading. Through this study the effect of fire exposed face, the effect of number of concrete segmental beam and the effect of concrete grade on the post fire behavior. Based on this parameter the pre-stressed force loss due to the applied load and also analyzing the energy absorption capacity of beam and getting numerically the load versus deflection curve and the crack width of segmental reinforced concrete beam investigated. Using ANSYS APDL software modeling of 81 samples for all the parametric study of investigating of post fire effect behavior on segmental concrete beam to get the numerical result and compare with the experimental result used for validation. According to the study, the increasing of heating temperature on the beam decrease the load carrying capacity by 51% from 300 to 700°C increasing the temperature load and 16.7 % from 300 to 500°c. Also, the number of segmental concrete beam decrease their ductility and stiffness. The other parameters like concrete grade and concrete cover are direct relation with the fire load but the segmental concrete beam exposed face has highly effect on the deflection and load carrying capacity. Keywords: Post tensioned, ductility, ANSYS, Segmental beam, Fire load