A stereocomplex membrane of isotactic and syndiotactic PMMA was prepared by mixing isotactic and syndiotactic resins synthesized separately at different conditions. The isotactic PMMA was polymerized anionically with Grignard reagent at -30℃ and the syndiotactic PMMA was polymerized radically in bulk by thermal and photochemical initiation at -50, 0, 25, 50 and 80℃. The tacticity was measured by 60MHz NMR and the molecular weight was measured by viscometry in chloroform solution at 25℃. Dope solution was formed by dissolving the two tactic PMMA resins in dimethyl sulfoxide, and the solution showed the thermoreversible sol-gel phase transition phenomena. The gel melting dehavior was observed by DSC to see the effect of the tacticity, polymer concentration in the dope, the tactic polymer ratio (isotactic/syndiotactic), and the molecular weight. The time and temperature dependence of the gelation process was also obserbed and the gelation kinetic equation was obtained in Avrami from. The effect of the same process parameters on the membranological properties was also observed from the dialysis and ultrafiltration tests. The water permeability decreased as the degree of stereocomplexity was increased but the solute permeability did not show any dependenece on the stereocomplex formation. Therefore, PMMA membranes which had the same solute permeability could be made to have different water permeabilities. The PMMA membranes showed higher water permeabilities than the cuprammonium cellulose membranes because of its hydrophobicity, although both membranes showed similar urea permeability. They showed higher solute permeabilities of the middle molecular weight substances, which is a good advantage in the biomedical application.