Due to freeze-thaw, dry-wet, salt intrusion and so on, the durability of hydraulic concrete which is of the long-distance water conveyance project in the saline areas of Northwest China has a negative influence, which directly affects the water conveyance stability and the operation safety and the benefit. In this paper, based on the water delivery structure of the Gansu Yinda-Qin project and accelerated indoor test, the changes of durability indexes such as mass loss rate, compressive strength loss rate and relative dynamic modulus of elasticity were studied for two working conditions: dry-wet-freeze-thaw cycle and dry-wet-freeze-thaw-salt invasion cycle. And the improved matter-element extension model was used to analyze the effects of four factors, namely, slag powder, fly ash, air-entraining agent and polypropylene, on the durability of hydraulic concrete. The influencing degree of four factors on the durability of hydraulic concrete was analyzed, and the calculated results were compared with the test results and the actual situations. The results show that in the dry-wet-freeze-thaw condition, the influence of fly ash on the durability of hydraulic concrete is more significant than that of slag powder, air entraining agent and polypropylene, while in the dry-wet-freeze-thaw-salt invasion condition, the influence of polypropylene is the most significant and sensitive. The improved matter-element extension model is used to comprehensively analyze the above four factors, and the influencing degree is polypropylene (3.450 9) > fly ash (2.509 0) > mineral powder (2.447 2) > engraver (2.232 5). According to the size of the characteristic value of the grade variable, the state of the concrete test block after large circulation can be judged, which is consistent with the actual situation. Therefore, the improved matter-element extension model can comprehensively analyze the influencing factors of the durability of hydraulic concrete in the saline areas and has certain practical value.