This paper designs an L-band four-channel T/ R module, which is used to amplify the signals sent and received by the antenna, and control the beam direction through changes in the channel phase shift amount. The paper introduces the design plan of this module, including structural design, index analysis, etc. The module adopts SIP high-integration design and consists of microwave circuits, control circuits, etc. It integrates functions such as negative pressure protection, power monitoring, standing wave detection, and temperature detection, and can be used in active phased array radars. The test results show that the T/ R module has good performance and has the advantage of stable operation.