This thesis concerns new developments within the orbital-free embedding theory, improvement of the existing functionals and design of the new algorithms facilitating multi-level simulations in condensed phase. Orbital free-embedding formalism is a theoretical method formulated within Density Functional Theory (DFT) which is used to study the effect of the environment on the electronic structure of chemical species embedded in condensed phase. Its principal ingredient is universal exact orbital-free embedding potential, which is uniquely defined by the pair of electron densities, the one corresponding to the embedded system, and the one corresponding to its environment. In this thesis the properties of the embedding potential are studied. The new approximation to the relevant density functional is proposed. The new algorithm to perform geometry optimization within orbital-free embedding formalism is given and tested on the set of benchmark weakly bound intermolecular complexes. The linearization approximation to the embedding potential is proposed to reduce the time of calculations for the large systems. Finally the statistical-mechanical theory of the liquids is applied to generate the average density of the environment, which is used to obtain average embedding potential. The adequacy of multi-level modeling scheme with average embedding potential is verified on calculations of solvent shifts for various chromophores.