Abstract: As a new structural material,FRP features light weight,high strength,corrosion resistance,etc.,and have a bright future when used for a new type of prestressing tendon in engineering structures.This paper introduced the calculation methods and calculation formulas of ultimate stress of unbonded tendons,and presented a simplified analytical method for unbonded prestressed FRP tendon.Compared with the tesed results of beams from reports,there are shown that the calculated results using above mentioned method are not only well agreed with tested results,but also can reflect the strucural mechanism for such kind of structures.