To increase the stability and bioavailability of Omeprazole(OMP), which is used newly as a proton-pump inhibitor, inclusion complex of OMP with $eta$-cyclodextrin($eta$-CD) was prepared by coprecipitation method and its characteristics were ascertained by means of solubility test, DSC, IR, and the accelerated stability analysis. The type of OMP inclusion complex is classified as Bs-type on phase solubility diagram, and the stoichiometric ratio of OMP: $eta$-CD complex is 1:2 and formation constant is 80.82/mole. The solubility of the complex could be increased remarkably by complexation compare with OMP. Degradation process of both OMP and OMP complex followed apparent first-order kinetics, of which degradation rate constants and activation energies are k$_{25}$=8.1$ imes$10$^{-4}$/day, E$_{a}$=22 Kcal/mole (OMP), and k$_{25}$=4.65$ imes$10$^{-6}$/day, E$_{a}$=35 Kcal/mole (complex), respectively. These results show the increase of the stability and solubility of OMP markedly, therefore it is believed that the improvement of stabilization for OMP by inclusion complexation might be practically available.