Water Storage and Controlled-release Film (WSCF) material is a kind of composite film which can form a “small reservoir” in the soil to meet the need of plant growth when packed with water and embedded in soil around tree roots. Coated water-transmitting fiber is a kind of functional fiber which has effect of transmitting water in WSCF material. Different coated water-transmitting fibers were prepared by treating natural fiber using colloidal composite materials made of polyvinyl alcohol and inorganic clay such as Common clay, Kaolin or Bentonite. Furthermore, the water-transmitting capacity and surface morphology of coated water-transmitting fibers were studied by thermal multi-analyzer, instrument for quick moisture measure and SEM. The results show that coated water-transmitting fiber with continuous and compact surface has better water-transmitting capacity than those with uneven surface and the addition amount of clay also can affect the water-transmitting capacity of coated fiber. Additionally, coated water-transmitting fibers can regulate water transferring according to the variation of temperature or soil humidity.