In order to knit a warp-knitted fabric with unidirectional wettability property, polyester multifilament and cotton yarn were used as raw materials, and samples were produced on an RD6 EL warp-knitting machine. The unidirectional wettability property of the fabric was tested by measuring the length of artificial sweat absorbed in the fabric. And the unidirectional wettability of the fabric primarily depends on the structure and twist of the yarn, especially the twist. The moisture absorption capacity of the yarn decreases with the yarn twist increasing. When the twist reaches a certain value, it will prevent the entry of moisture. This provides us with an inspiration for controlling the moisture absorption of fabric by the twist of the yarn when knitting the unidirectional wettability fabric.