The paper deals with the perturbation techniques for dynamic systems described by differential inclusions and state constraint relations. We replace the phase restrictions by a new differential inclusion with a small parameter multiplying the derivative and study the limit behaviour of the system combining two groups of differential inclusions, the former to be the given differential inclusion and the latter to be the introduced one. The idea based upon consideration of all matrix time-varying perturbations to this system allows one to describe the attainability sets of the primary differential inclusion under state constraints. Applications to the control and observation problems are also discussed.