Silicone elastomers filled by fumed silica reveal peculiar technical behaviour, Chemical modification of the silica surface is commonly used to control the rheological and mechanical properties of uncured and cross-linked silicone elastomers. To study the microscopic aspect of the problem. quantum-chemical (QCh) modelling in the framework, of originally elaborated semiempirical techniques has been performed. The response of a silicone polymer fragment, interacting with a silica model cluster, to external stress is considered in terms of a mechanochemical reaction. The impact of silicone-water and silicone-modified filler interactions on stress-strain characteristics, i.e. Young's modulus, energy and force of deformation and tensile strength have been studied on a molecular level.