As the way of arranging circular prestress tendons in the PC (Prestressed Concrete) pylon anchorage zones of cable-stayed bridges has its disadvantages in terms of mechanical performance and construction，a new arrangement of prestress tendons by the name of one-way straight tendons is put forward． Under this kind of arrangement，the prestress tendons are relatively short，and their prestress loss laws and construction control are different from the tendons with common length． In order to investigate the loss characteristic of this kind of short straight prestress tendons，the friction loss (the duck friction and the anchorage friction) and the loss due to anchorage set as well as the elongation control are emphatically analyzed by a full-scale model test． Moreover，the prestress tendons under anchor are observed for a short time． The results show that (1) the average total loss of prestress is 26%;(2) in the total loss，the loss due to anchorage set，the duct friction loss and the anchorage head friction loss respectively account for more than 50%，about 12% and 20%，and the latter two types of loss should not be ignored as most articles and codes have recommended; and (3) the elongation control is still applicable in the construction of short prestress tendons，but in view of its exquisite sensitivity to the construction error，the construction quality must be guaranteed and the permissible error should be extended to ±9%．