Polyester has the highest share of world fibre market, which also leads to a large volume of polyester waste. In this study, a compact process combining alkali treatment and stone milling was used to recycle waste polyester fibre into ultrafine powder efficiently. The morphology of the original polyester fibre, alkali modified fibre and milled polyester powder were observed by Scanning electronic microscopy (SEM) and atomic force microscope (AFM). The particle size, crystallinity and strength loss were also studied. It was found that the alkali treatment greatly reduced fibre strength and the crystallinity of the fibre largely decreased after stone milling. The waste polyester fibre was converted into micron powders easily and efficiently. About 700 g dry ultrafine powders with particle size of around 60 µm were achieved in 2 h. This method shows a great potential for industrial application of waste polyester in the future.