In this work we have investigated exciton properties of Si quantum dots (QD) imbedded into the SiO2 dielectric medium. The influence of different QD shapes (spherical, coupled truncated pyramids and coupled spherical) on the exciton states has been investigated. We have calculated quantized electron and hole energy spectra in the framework of effective mass theory, using one-band Hamiltonian for electrons and three-band Hamiltonian for holes. The calculations of the exciton energy have been done in the framework of the first order perturbation theory:  formula where gap E is the energy gap in Si; ne Ee and nh Eh are the size-quantized electron and hole energies respectively; binding E is the exciton binding energy. The binding exciton energy was calculated taking into account the difference between dielectric permittivity of the QD and surrounding medium. We have investigated dependence of exciton energy on QD’s volume for spherical and coupled truncated pyramids QDs and on the distance for coupled spheres QDs between centers of each sphere. We have obtained higher energies for coupled truncated pyramids then for spherical QDs. The dependence of exciton energy on the distance between centers for coupled spheres QDs has the minimum at the medium distances (distances have been varied from 0 to 2R)