In this paper, we propose a new balancing coordinate for the continuous-time system embedded in a sampleddata system which is a natural extension of the frequency weighted balanced realization of the continuous-time system to incorporate hybrid input and output weights. We show that the matrix which transforms the coordinate of the continuous-time system to the balanced coordinate can be calculated from the weighted controllability grammian and the weighted observability grammian. We then apply the new balanced truncation method to the problem of plant reduction for sampled-data systems, and an algorithm is proposed for obtaining a low order discrete-time controller by plant reduction based on a successive approximation. A numerical example illustrates the advantage of the proposed method.