Based on the static load test results of nine externally prestressed concrete beams, a simplified calculation method for the moment, stiffness and stress increment of external tendons at the ultimate state of externally prestressed concrete beams is established. Meanwhile, this method is used to analyze and calculate the test results of a batch of externally prestressed concrete beams abroad, with good results obtained. It is proved that the method has strong generality and good calculation accuracy, and provides a directly usable formula for the research and design of various externally prestressed structures.