To obtain fluid production parameters from various production zones downhole while controlling fluid flow, we developed a new intelligent completion system that simultaneously regulated multilayer production using a single-core cable and two hydraulic lines. In this study, an integrated downhole tool for the new intelligent completion system, integrating a multiparameter monitoring system, a hydraulic switching system, and a flow control valve. According to the requirement specifications of the tool, we designed a downhole monitoring circuit module, a downhole hydraulic switching control circuit module, and a downhole communication module, and we developed an associated host computer. Surface testing of the tool prototype indicated that the tool performed multiparameter fluid measurement, hydraulic switching control, bidirectional signal transmission, and hydraulic actuation of the flow control valve. The surface monitoring platform was able to acquire formation parameter data in real time and facilitated smooth communication. This system met the downhole operation requirements, thus achieving the three main functions of measurement, control, and transmission required in intelligent completion. These results further enhance China’s intelligent completion technology framework.