The invention relates to a measuring method and a device for apparent fluffing and balling as well as abrasion loss of a yarn. The device comprises a yarn winding mechanism with a yarn grinding function, a yarn grinding mechanism with controllable friction pressure, a yarn feed mechanism with adjustable tension, a static and clipping mechanism, a hair bulb and hair feather collection mechanism, an optical measuring system for instant observation of yarn sample fluffing and balling shape and quantity, a data acquisition and control system and a computer. The method comprises the steps that the hair feather significance, the hair bulb shape and the hair bulb quantity of the yarn are immediately measured after a yarn sample is formed by winding the yarn through equal-tension close packing; friction fluffing and balling sampling is performed; and the hair feather significance, the hair bulb quantity, the hair feather and hair bulb abrasion, and the hair feather and hair bulb maintenance quantity of a yarn grinding sample in a process and in a final state are measured synchronously. The device is ingenious and practical in structure, and takes measurements precisely and quantitatively, the in-situ measuring device and the method are multipurpose, can measure multiple indexes, can be used for comprehensive evaluation of the yarn fluffing significance, the balling quantity and shape, the abrasion fiber quantity, the fluffing resistance, and the balling resistance, and can also be used for estimating fluffing and balling grades of fabric.