This paper considers the problem of L-p stability checking for a feedback uncertain system which consists of a linear plant in its forward loop and non-linear uncertain dynamics in its feedback loop. It is supposed that the non-linear part of the system is of dynamic uncertainties characterized by a certain set of constraints. The concepts used here are the well-posedness of the feedback system and the norm constraint for the feedback uncertainties, leading to a sufficient condition for robust stability. The result is illustrated to be efficient through an example.