To reduce the highly hydrophilic property of chondroitin sulfate (ChS). a semi-interpenetrating polymer network (semi-IPN) of chondroitin sulfate/polyacrylic acid (PAA) was prepared as a drug carrier by crosslinking acrylic acid with diethyleneglycol diacrylate. The swelling properties of the semi-IPNs with different concentrations of crosslinking agent were correlated. The moisture sorption profiles were evaluated using differential thermal analysis. Ketoprofen was used as a drug probe to evaluate the performance of the drug released from the semi-IPN matrices. The prepared semi-IPNs demonstrated significant swelling reduction properties with both gastric and intestinal fluids compared with those of both the pure ChS and the ChSAA blend without the crosslinking agent. The amount of accumulated drug released from the semi-IPNs was less than 30 wt % at pH 1.2 and up to 80 wt % at pH 7.4.