The bearing capacity of bridge structure would decrease under high temperature in fire, and there is a risk of structural collapse when the bearing capacity decreased to a certain degree. The estimate of bearing capacity of concrete structure at high temperature in fire will directly influence the scheme of disaster relief. Recently, there are a few researches on evaluating the bearing capacity of concrete structure at high temperature in fire, even fewer on bearing capacity of prestressed structure. Surface temperature and temperature of internal specific position of prestressed concrete T-beam are put forward in this paper by making use of ISO 834 international standard heating curve and distribution rules of temperature field of ASCE. The degradation of mechanical properties of concrete, steel bar, steel strand and other materials at high temperature are worked out according to relationships between material mechanical properties and high temperature, and on this basis, the bearing capacity of 3 prestressed concrete T-beams are calculated and evaluated at high temperature in fire. The results show that after being under 3-hour's high temperature in fire, the bearing capacity in high temperature of prestressed concrete T-beam would decreased to it’s 25% in normal; the stronger the concrete is or the thinner the concrete cover is, the greater decrease of bearing capacity of prestressed concrete T-beam would be. Based on calculations and evaluations, a statistics regression equation of bearing capacity of prestressed concrete T-beam at high temperature in fire is obtained.