In this paper, poly(ϵ-caprolactone)-graft-carboxylic acid (P(α-C2CL)) was prepared via a thio-bromo click reaction between mercaptosuccinic acid and poly(α-bromo-ϵ-caprolactone). It is readily soluble in aqueous solutions (pH 5.5–9.8) due to the presence of carboxylic groups in each repeating unit. A series of water-soluble P(α-C2CL)-paclitaxel prodrugs with high drug contents (up to 41.4 wt-%) was prepared by esterification. Meanwhile, methyl tetrazolium (MTT) assays showed that P(α-C2CL)-paclitaxel prodrugs exhibited a high antitumour effect on A549 and MCF-7 cells. These prodrugs have appeared as a highly versatile and potent platform for cancer therapy.