Abstract: This paper concerns the robust passive control problem for linear systems with time- varying uncertain parameters under bounded energy exogenous inputs. The objective is to design a feedback control law such that the closed-loop system is both quadratically stable and strictly passive for all the admissible uncertainties. It is shown that such a problem is equivalent to a positive real control problem for a certain linear time-invariant system with a positive scaling parameter. Thus, a complete solution to such a problem can be achieved by using the existing results of standard positive real control problem.