Abstract: Background The improvement mechanisms of hydraulic characteristics in cement-based habitat substrate remain unclear. Although fiber modification is a mature technology for substrate enhancement, how different fibers influence the hydraulic properties of the substrate is still not well understood. This study investigates the effects of polypropylene fiber, basalt fiber, and palm fiber on the hydraulic characteristics of cement-based habitat substrate and clarifies their functional differences in regulating hydraulic performance. Methods Laboratory experiments were conducted to analyze the effects of incorporating polypropylene fiber, basalt fiber, and palm fiber on substrate volumetric weight, pore structure, saturated water content, saturated hydraulic conductivity, soil-water characteristic curve, and soil column infiltration process. All fibers were added at 0.4% of the dry mix mass. The underlying clay layer was obtained from an expansive soil site in Guangxi, China. Scanning electron microscopy was used to observe the microstructure. Model fitting was performed using the power function, linear function, Kostiakov model, Philip model, and Horton model. The soil-water characteristic curve was measured using the filter paper method with 10 sample groups at moisture gradients from 4% to 22%. Results All three fiber types reduced volumetric weight and total porosity. Palm fiber increased capillary porosity by 4.43%. Polypropylene fiber and basalt fiber increased the air-to-water ratio by 12.23% and 13.02%, respectively. Polypropylene fiber and basalt fiber increased saturated hydraulic conductivity, while palm fiber decreased it. All soil-water characteristic curves showed three stages: boundary effect (0-200 kPa), transition (200-4000 kPa), and residual (>4000 kPa). Fiber incorporation improved water retention capacity. The basalt fiber and palm fiber groups showed decreased air-entry values. The palm fiber group exhibited the highest residual water content. The infiltration process had three stages: transient (0-5 min), gradual (5-20 min), and stable (>20 min). All three fibers slowed wetting front advancement and reduced cumulative infiltration. Infiltration resistance ranked as: palm fiber > polypropylene fiber > basalt fiber. Compared with the control, the palm fiber group increased total infiltration time by 109.7%. At the end of infiltration, cumulative infiltration decreased by 17.6% for polypropylene fiber, 9.8% for basalt fiber, and 43.1% for palm fiber. Initial infiltration rates decreased by 11.8%, 25.4%, and 55.9% for polypropylene fiber, basalt fiber, and palm fiber groups, respectively. The power function effectively described the wetting front and cumulative infiltration. The linear function adequately described wetting front changes in the underlying clay layer. The Kostiakov model provided the best fit for the entire infiltration process. Conclusions Palm fiber enhances water retention capacity by increasing capillary porosity, resulting in lower permeability and higher residual water content. It is suitable for substrates requiring high water retention. Polypropylene fiber and basalt fiber improve saturated hydraulic conductivity by increasing the air-to-water ratio and pore connectivity, enhancing water transmission capacity. They are suitable for engineering scenarios requiring rapid drainage. The regulation pathways of hydraulic characteristics differed among fiber types. Fiber selection should be optimized based on engineering requirements. This study provides a theoretical basis for targeted fiber application to regulate hydraulic characteristics of cement-based habitat substrates in ecological restoration projects