Summary The effects of xylanase–cellulase hydrolysis, ultrasonic modification and enzymatic‐ultrasonic treatment on the physicochemical properties, morphological structures and adsorption capacities in vitro of purified fibre (PF) from tea seed were determined. The results showed the ultrasonically treated fibre (UTF) had a higher water‐holding capacity (60.15 g g−1), oil‐binding capacity (30.42 g g−1), swelling capacity (29.93 mL g−1), emulsification activity (381.36 m2 g−1) and emulsification stability (20.20) than PF, enzymatically hydrolysed fibre (EHF) and enzymatic‐ultrasonic treated fibre (EUF). The structures of PF, UTF, EHF and EUF were characterised by scanning electron microscope, Laser particle size analyzer, X‐ray diffraction, thermogravimetric analysis and Fourier transform infrared spectra. Furthermore, compared with PF, the adsorption capacity of UTF, EHF and EUF for cholesterol, glucose and nitrite ions during simulative gastrointestinal tract was improved to different degrees. This study can provide guidance for the comprehensive utilisation of byproduct of tea seed and designing novel functional dietary fibre.