Abstract: The head loss characteristics of trashrack, considering the blockage of trashrack and the rust of its single rack bars, are studied by applying hydraulic model test based on Fengman Hydropower Station. It has shown that the head loss increase rises by 60 percent as the rack bars rusted, the head loss increasing rapidly with blockage of trashrack increasing, and the increase of head loss in this case would rise 200 percent, correspondingly, the ratio of blockage is 62.5 percent. Finally, the experimental data obtained from the test was used to modify the expression on the efficient of head loss proposed by experts from former Soviet Union, and a modifier formula is presented in this paper for the calculation of total head loss of trashrack. A suggestion of 3～5 meters head loss was come up for the design of trashrack in hydropower stations.