Service-Oriented Computing (SOC) is a promising means to integrate heterogeneous systems. Services from different providers can be integrated into a composite service regardless of their locations, platforms, and/or execution speeds to implement complex business processes. In this paper we propose an approach for the services composition that takes into account the QoS that the composite system must satisfy. After that we design the service selection algorithm used to construct the optimal composite service with the objective to maximize the values of the well-defined QoS characteristics. In this paper we are interested on the Data-Intensive applications where the QoS attributes are very important for the reliability and performance of these systems.