Pectin is a polysaccharide that widely exists in plant cell walls and has a variety of physiologically active functions. Various studies have confirmed that modification of polysaccharide can improve its biological activity. Therefore， in this study， the citrus segment membrane pectin (PP) and its degraded oligosaccharides (POS1 and POS2) recovered from the citrus canning waste water were carried out sulfate esterification in order to increase their activity. Molecular weight and monosaccharide composition analysis showed that after sulfating by TBA and DMSO systems， the molecular weight of sulfated pectin polysaccharides and oligosaccharides were decreased， and the content of arabinose and galactose reduced significantly. FTIR and NMR results shown that the H4 of each component of galacturonic acid showed a low-field shift after sulfation. And the anomer hydrogen signals of galactose and arabinose from POS1 and POS2 shifted to the low field， respectively. Which indicating that the main chain and the side chain were sulfated. The in vitro results showed that the anti-tumor activity of sulfated POS1 and POS2 was further enhanced. Among them， POS1-T has the best effect， with an inhibition rate of 30.25%. In summary， the results of the study indicated that sulfation could increase the antitumor effect of pectin polysaccharide and its oligosaccharides.