In this paper, it was investigated that the effect of parameters such as the ionic strength, pH, counter-ion type of release medium, particle size, and cross linkage of cation exchange resin on the release of model drug pseudoephedrine hydrochloride (PE) from uncoated drug-resin complex. The drug-resin complex was prepared by the reaction of PE with strongly acidic cation exchange resin (001×4, 001×7, 001×14). The result showed that the loading of PE increased with the increase of temperatures. The release of PE from drug-resin complex at 37℃ was monitored in vitro. From the experiments, it was found that the release rate of PE depends on the pH, composition of the releasing media, increased at lower pH media or with increase of ionic strength of media. Moreover, the release rate of PE was inversely proportional to the cross-linkage and particle size of the cation exchange resin. In this paper, it was investigated that the effect of parameters such as the ionic strength, pH, counter-ion type of release medium, particle size, and cross linkage of cation exchange resin on the release of model drug pseudoephedrine hydrochloride (PE) from uncoated drug-resin complex. The drug-resin complex was prepared by the reaction of PE with a slightly acidic cation exchange resin (001 × 4, 001 × 7, 001 × 14). The result showed that the loading of PE increased with the increase of temperatures. The release of PE from drug-resin complex at 37 ° C was monitored in vitro. From the experiments, it was found that the release rate of PE depends on the pH, composition of the releasing media, increased at lower pH media or with increase of ionic strength of media. However, the release rate of PE was inversely proportional to the cross-linkage and particle size of the cation exchange resin.