Abstract: In order to solve the problem that the width of concrete crack outside the steel-lined reinforced concrete pressure pipe exceeds the design limit,the method of mixing polypropylene fiber into concrete is considered.Based on the large model test of the steel-lined reinforced concrete pressure pipeline of Three Gorges Hydropower Station,a 3D finite element model was established to research the influence of different polypropylene fibers on the concrete crack characteristics of pressure pipeline.The concrete plastic damage model was used to simulate the damage process of the outer concrete of the concrete pressure pipe mixed with polypropylene fiber under the action of internal water pressure.The results show that mixing coarse polypropylene fiber or coarse fine mixed fiber can limit the development of concrete cracks outside the pressure pipeline,and the cracking load of the pipeline is significantly increased.Under the effect of internal water pressure,the number of penetrating cracks in the pressure pipeline with polypropylene crude fiber or coarse and fine mixed fiber decreases.The stress of steel decreases with the increase of polypropylene fiber content.