Micro-porous osmotic controlled release tablets of a poorly water-soluble drug were prepared to investigate the controlled release of the drug.Lamotrigine, an antiepileptic drug, was chosen as a model drug because of its severe side-effects, primarily leading to the rapid increase in blood plasma levels after each dose of existing marketed tablet (immediate release compositions).HPMC E4M/K100 LV CR (3∶1) were used in sustained release matrix tablets due to its relatively low viscosity and could be swelling in water to prevent the drug from releasing.Eudragit L100-55/PVA (5∶1) were used in coating composition of tablet to prevent the drug releasing from tablets in stomach.PVA was used as pore former to modify drug releasing.The in-vitro investigation of the tablet was performed in 0.01mol/L HCL acid media 2 hours and pH6.8 phosphate buffered solution(PBS) containing 0.5%SDS 16 hours with apparatus Ⅱ according to CP2010 combined with HPLC analysis.Micro-porous osmotic controlled release tablets showed the drug could be completely released from tablets in media mentioned above.The drug release of tablet was dependent on the type of HPMC and the amount of PVA and coating weight.The release rate showed good fit with Zero-order model and the release of drug from the tablets might be due to combination of water uptake, diffusing, swelling and erosion.The study demonstrated that micro-porous osmotic tablets based on mixtures of HPMC, Eudragit L100-55 and PVA showed good controlled release performance.