The present invention provides a lossless monitoring socket. The present invention provides a circuit board, a first spring, a second spring, a measuring head, a signal monitoring module and a reflective switch. The first spring and the second spring are located on the circuit board; the first spring is connected with the Ctrl pin of the reflective switch, and the second spring is connected with an earth point; the reflective switch is connected with the signal monitoring module; and the measuring head is inserted in the circuit board and touches the first spring and the second spring. The monitoring socket reduces the insertion loss of the monitoring part and realizes low TV insertion loss and high DS output level. The monitoring socket is able to control and monitor the switch on the circuit so as to allow the TV insertion loss to reduce 1dB. The lossless monitoring socket is used as the route usage without changing the user's usage habit and is convenient to use. The switch device is small in size without any influence on the layout of an original design. The lossless monitoring socket is simple and reliable in structure and low in cost.