A loopback test starting system is provided for starting a loopback test. The loopback test starting system includes a first loopback controller which detects a first loopback control signal from a digital data services network side and generates a first loopback starting signal. In addition, a second loopback controller is provided which detects a second loopback control signal from a subscriber side and generates a second loopback starting signal in response. The loopback test starting system also includes a first loopback forming device which forms a first loop from the digital data services network side through the subscriber side and back to the digital data services network side, and a second loopback forming device which forms a second loop from the subscriber's side through the digital data services side and back to the subscriber side. Further, the loopback testing starting system includes first and second loopback detection and resetting devices for resetting and stopping the detection operations of the first and second loopback controllers. Based on this above configuration, the loopback test starting system is able to avoid a loopback closed circuit with out prohibiting a loopback test from the subscriber's side, thus improving the quality of the maintenance control of the entire network.