The invention discloses a sampling mechanism suitable for detecting the water absorbing capacity of a fiber material. The sampling mechanism comprises an open-ended cup, a sampling rod, a cup cover, aconnecting cylinder, a positioning cylinder and a flexible connecting strip, the upper end of the open-ended cup is open, the positioning cylinder is embedded in the open-ended cup and is in interference fit with the open-ended cup, and the upper end of the sampling rod is connected with the positioning cylinder; the lower end of the connecting cylinder is connected with the upper end of the positioning cylinder, and the bottom of the connecting cylinder is in contact with the edge of the opening of the upper end of the open-ended cup; the cup cover is connected with the connecting cylinder through the flexible connecting strip, and the opening of the upper end of the connecting cylinder is sealed with the cup cover; and the sidewall of the upper end of the connecting cylinder protrudes to form an annular positioning protrusion, the cup cover is provided with a positioning groove different from the annular positioning protrusion in sizes and shapes, and the annular positioning protrusion is embedded in the positioning groove when the connecting cylinder is sealed with the cup cover. The sampling mechanism is used for sampling and placing the fiber material, and can avoid the sampled fiber material from being polluted.