Abstract: The mechanical analysis is carried out for the preliminary designof the pipeline crossing diagonal cable type structure in Mulong River by thefinite-element method. The results indicate that the cable with some pre-strain can improve the strength and the stiffness of thestructure while it is installed, but if the pre-strain is too largethe strength and the stiffness will be declined, so there is an optimum value ofpre-strain for the structure, to be influenced by the form of structureand the loads on structure; under the work loads or the water filling loads,the strength of the structure just meets the requirements. Under the ultimateloads, the strength of the structure does not meet the requirements. There arethree places where the maximum stress is reached in the structure theleft tower top connected with cable, the right tower top connected withcable and the upper limb of the intermediate pipe bridge.